drm/i915/execlists: Protect peeking at execlists->active

[linux.git] / drivers / gpu / drm / i915 / gt / intel_lrc.c

/*
 * Copyright © 2014 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 * Authors:
 *    Ben Widawsky <ben@bwidawsk.net>
 *    Michel Thierry <michel.thierry@intel.com>
 *    Thomas Daniel <thomas.daniel@intel.com>
 *    Oscar Mateo <oscar.mateo@intel.com>
 *
 */

/**
 * DOC: Logical Rings, Logical Ring Contexts and Execlists
 *
 * Motivation:
 * GEN8 brings an expansion of the HW contexts: "Logical Ring Contexts".
 * These expanded contexts enable a number of new abilities, especially
 * "Execlists" (also implemented in this file).
 *
 * One of the main differences with the legacy HW contexts is that logical
 * ring contexts incorporate many more things to the context's state, like
 * PDPs or ringbuffer control registers:
 *
 * The reason why PDPs are included in the context is straightforward: as
 * PPGTTs (per-process GTTs) are actually per-context, having the PDPs
 * contained there mean you don't need to do a ppgtt->switch_mm yourself,
 * instead, the GPU will do it for you on the context switch.
 *
 * But, what about the ringbuffer control registers (head, tail, etc..)?
 * shouldn't we just need a set of those per engine command streamer? This is
 * where the name "Logical Rings" starts to make sense: by virtualizing the
 * rings, the engine cs shifts to a new "ring buffer" with every context
 * switch. When you want to submit a workload to the GPU you: A) choose your
 * context, B) find its appropriate virtualized ring, C) write commands to it
 * and then, finally, D) tell the GPU to switch to that context.
 *
 * Instead of the legacy MI_SET_CONTEXT, the way you tell the GPU to switch
 * to a contexts is via a context execution list, ergo "Execlists".
 *
 * LRC implementation:
 * Regarding the creation of contexts, we have:
 *
 * - One global default context.
 * - One local default context for each opened fd.
 * - One local extra context for each context create ioctl call.
 *
 * Now that ringbuffers belong per-context (and not per-engine, like before)
 * and that contexts are uniquely tied to a given engine (and not reusable,
 * like before) we need:
 *
 * - One ringbuffer per-engine inside each context.
 * - One backing object per-engine inside each context.
 *
 * The global default context starts its life with these new objects fully
 * allocated and populated. The local default context for each opened fd is
 * more complex, because we don't know at creation time which engine is going
 * to use them. To handle this, we have implemented a deferred creation of LR
 * contexts:
 *
 * The local context starts its life as a hollow or blank holder, that only
 * gets populated for a given engine once we receive an execbuffer. If later
 * on we receive another execbuffer ioctl for the same context but a different
 * engine, we allocate/populate a new ringbuffer and context backing object and
 * so on.
 *
 * Finally, regarding local contexts created using the ioctl call: as they are
 * only allowed with the render ring, we can allocate & populate them right
 * away (no need to defer anything, at least for now).
 *
 * Execlists implementation:
 * Execlists are the new method by which, on gen8+ hardware, workloads are
 * submitted for execution (as opposed to the legacy, ringbuffer-based, method).
 * This method works as follows:
 *
 * When a request is committed, its commands (the BB start and any leading or
 * trailing commands, like the seqno breadcrumbs) are placed in the ringbuffer
 * for the appropriate context. The tail pointer in the hardware context is not
 * updated at this time, but instead, kept by the driver in the ringbuffer
 * structure. A structure representing this request is added to a request queue
 * for the appropriate engine: this structure contains a copy of the context's
 * tail after the request was written to the ring buffer and a pointer to the
 * context itself.
 *
 * If the engine's request queue was empty before the request was added, the
 * queue is processed immediately. Otherwise the queue will be processed during
 * a context switch interrupt. In any case, elements on the queue will get sent
 * (in pairs) to the GPU's ExecLists Submit Port (ELSP, for short) with a
 * globally unique 20-bits submission ID.
 *
 * When execution of a request completes, the GPU updates the context status
 * buffer with a context complete event and generates a context switch interrupt.
 * During the interrupt handling, the driver examines the events in the buffer:
 * for each context complete event, if the announced ID matches that on the head
 * of the request queue, then that request is retired and removed from the queue.
 *
 * After processing, if any requests were retired and the queue is not empty
 * then a new execution list can be submitted. The two requests at the front of
 * the queue are next to be submitted but since a context may not occur twice in
 * an execution list, if subsequent requests have the same ID as the first then
 * the two requests must be combined. This is done simply by discarding requests
 * at the head of the queue until either only one requests is left (in which case
 * we use a NULL second context) or the first two requests have unique IDs.
 *
 * By always executing the first two requests in the queue the driver ensures
 * that the GPU is kept as busy as possible. In the case where a single context
 * completes but a second context is still executing, the request for this second
 * context will be at the head of the queue when we remove the first one. This
 * request will then be resubmitted along with a new request for a different context,
 * which will cause the hardware to continue executing the second request and queue
 * the new request (the GPU detects the condition of a context getting preempted
 * with the same context and optimizes the context switch flow by not doing
 * preemption, but just sampling the new tail pointer).
 *
 */
#include <linux/interrupt.h>

#include "gem/i915_gem_context.h"

#include "i915_drv.h"
#include "i915_perf.h"
#include "i915_trace.h"
#include "i915_vgpu.h"
#include "intel_engine_pm.h"
#include "intel_gt.h"
#include "intel_gt_pm.h"
#include "intel_lrc_reg.h"
#include "intel_mocs.h"
#include "intel_reset.h"
#include "intel_workarounds.h"

#define RING_EXECLIST_QFULL             (1 << 0x2)
#define RING_EXECLIST1_VALID            (1 << 0x3)
#define RING_EXECLIST0_VALID            (1 << 0x4)
#define RING_EXECLIST_ACTIVE_STATUS     (3 << 0xE)
#define RING_EXECLIST1_ACTIVE           (1 << 0x11)
#define RING_EXECLIST0_ACTIVE           (1 << 0x12)

#define GEN8_CTX_STATUS_IDLE_ACTIVE     (1 << 0)
#define GEN8_CTX_STATUS_PREEMPTED       (1 << 1)
#define GEN8_CTX_STATUS_ELEMENT_SWITCH  (1 << 2)
#define GEN8_CTX_STATUS_ACTIVE_IDLE     (1 << 3)
#define GEN8_CTX_STATUS_COMPLETE        (1 << 4)
#define GEN8_CTX_STATUS_LITE_RESTORE    (1 << 15)

#define GEN8_CTX_STATUS_COMPLETED_MASK \
         (GEN8_CTX_STATUS_COMPLETE | GEN8_CTX_STATUS_PREEMPTED)

#define CTX_DESC_FORCE_RESTORE BIT_ULL(2)

#define GEN12_CTX_STATUS_SWITCHED_TO_NEW_QUEUE  (0x1) /* lower csb dword */
#define GEN12_CTX_SWITCH_DETAIL(csb_dw) ((csb_dw) & 0xF) /* upper csb dword */
#define GEN12_CSB_SW_CTX_ID_MASK                GENMASK(25, 15)
#define GEN12_IDLE_CTX_ID               0x7FF
#define GEN12_CSB_CTX_VALID(csb_dw) \
        (FIELD_GET(GEN12_CSB_SW_CTX_ID_MASK, csb_dw) != GEN12_IDLE_CTX_ID)

/* Typical size of the average request (2 pipecontrols and a MI_BB) */
#define EXECLISTS_REQUEST_SIZE 64 /* bytes */
#define WA_TAIL_DWORDS 2
#define WA_TAIL_BYTES (sizeof(u32) * WA_TAIL_DWORDS)

struct virtual_engine {
        struct intel_engine_cs base;
        struct intel_context context;

        /*
         * We allow only a single request through the virtual engine at a time
         * (each request in the timeline waits for the completion fence of
         * the previous before being submitted). By restricting ourselves to
         * only submitting a single request, each request is placed on to a
         * physical to maximise load spreading (by virtue of the late greedy
         * scheduling -- each real engine takes the next available request
         * upon idling).
         */
        struct i915_request *request;

        /*
         * We keep a rbtree of available virtual engines inside each physical
         * engine, sorted by priority. Here we preallocate the nodes we need
         * for the virtual engine, indexed by physical_engine->id.
         */
        struct ve_node {
                struct rb_node rb;
                int prio;
        } nodes[I915_NUM_ENGINES];

        /*
         * Keep track of bonded pairs -- restrictions upon on our selection
         * of physical engines any particular request may be submitted to.
         * If we receive a submit-fence from a master engine, we will only
         * use one of sibling_mask physical engines.
         */
        struct ve_bond {
                const struct intel_engine_cs *master;
                intel_engine_mask_t sibling_mask;
        } *bonds;
        unsigned int num_bonds;

        /* And finally, which physical engines this virtual engine maps onto. */
        unsigned int num_siblings;
        struct intel_engine_cs *siblings[0];
};

static struct virtual_engine *to_virtual_engine(struct intel_engine_cs *engine)
{
        GEM_BUG_ON(!intel_engine_is_virtual(engine));
        return container_of(engine, struct virtual_engine, base);
}

static int __execlists_context_alloc(struct intel_context *ce,
                                     struct intel_engine_cs *engine);

static void execlists_init_reg_state(u32 *reg_state,
                                     struct intel_context *ce,
                                     struct intel_engine_cs *engine,
                                     struct intel_ring *ring);

static inline u32 intel_hws_preempt_address(struct intel_engine_cs *engine)
{
        return (i915_ggtt_offset(engine->status_page.vma) +
                I915_GEM_HWS_PREEMPT_ADDR);
}

static inline void
ring_set_paused(const struct intel_engine_cs *engine, int state)
{
        /*
         * We inspect HWS_PREEMPT with a semaphore inside
         * engine->emit_fini_breadcrumb. If the dword is true,
         * the ring is paused as the semaphore will busywait
         * until the dword is false.
         */
        engine->status_page.addr[I915_GEM_HWS_PREEMPT] = state;
        if (state)
                wmb();
}

static inline struct i915_priolist *to_priolist(struct rb_node *rb)
{
        return rb_entry(rb, struct i915_priolist, node);
}

static inline int rq_prio(const struct i915_request *rq)
{
        return rq->sched.attr.priority;
}

static int effective_prio(const struct i915_request *rq)
{
        int prio = rq_prio(rq);

        /*
         * If this request is special and must not be interrupted at any
         * cost, so be it. Note we are only checking the most recent request
         * in the context and so may be masking an earlier vip request. It
         * is hoped that under the conditions where nopreempt is used, this
         * will not matter (i.e. all requests to that context will be
         * nopreempt for as long as desired).
         */
        if (i915_request_has_nopreempt(rq))
                prio = I915_PRIORITY_UNPREEMPTABLE;

        /*
         * On unwinding the active request, we give it a priority bump
         * if it has completed waiting on any semaphore. If we know that
         * the request has already started, we can prevent an unwanted
         * preempt-to-idle cycle by taking that into account now.
         */
        if (__i915_request_has_started(rq))
                prio |= I915_PRIORITY_NOSEMAPHORE;

        /* Restrict mere WAIT boosts from triggering preemption */
        BUILD_BUG_ON(__NO_PREEMPTION & ~I915_PRIORITY_MASK); /* only internal */
        return prio | __NO_PREEMPTION;
}

static int queue_prio(const struct intel_engine_execlists *execlists)
{
        struct i915_priolist *p;
        struct rb_node *rb;

        rb = rb_first_cached(&execlists->queue);
        if (!rb)
                return INT_MIN;

        /*
         * As the priolist[] are inverted, with the highest priority in [0],
         * we have to flip the index value to become priority.
         */
        p = to_priolist(rb);
        return ((p->priority + 1) << I915_USER_PRIORITY_SHIFT) - ffs(p->used);
}

static inline bool need_preempt(const struct intel_engine_cs *engine,
                                const struct i915_request *rq,
                                struct rb_node *rb)
{
        int last_prio;

        if (!intel_engine_has_semaphores(engine))
                return false;

        /*
         * Check if the current priority hint merits a preemption attempt.
         *
         * We record the highest value priority we saw during rescheduling
         * prior to this dequeue, therefore we know that if it is strictly
         * less than the current tail of ESLP[0], we do not need to force
         * a preempt-to-idle cycle.
         *
         * However, the priority hint is a mere hint that we may need to
         * preempt. If that hint is stale or we may be trying to preempt
         * ourselves, ignore the request.
         */
        last_prio = effective_prio(rq);
        if (!i915_scheduler_need_preempt(engine->execlists.queue_priority_hint,
                                         last_prio))
                return false;

        /*
         * Check against the first request in ELSP[1], it will, thanks to the
         * power of PI, be the highest priority of that context.
         */
        if (!list_is_last(&rq->sched.link, &engine->active.requests) &&
            rq_prio(list_next_entry(rq, sched.link)) > last_prio)
                return true;

        if (rb) {
                struct virtual_engine *ve =
                        rb_entry(rb, typeof(*ve), nodes[engine->id].rb);
                bool preempt = false;

                if (engine == ve->siblings[0]) { /* only preempt one sibling */
                        struct i915_request *next;

                        rcu_read_lock();
                        next = READ_ONCE(ve->request);
                        if (next)
                                preempt = rq_prio(next) > last_prio;
                        rcu_read_unlock();
                }

                if (preempt)
                        return preempt;
        }

        /*
         * If the inflight context did not trigger the preemption, then maybe
         * it was the set of queued requests? Pick the highest priority in
         * the queue (the first active priolist) and see if it deserves to be
         * running instead of ELSP[0].
         *
         * The highest priority request in the queue can not be either
         * ELSP[0] or ELSP[1] as, thanks again to PI, if it was the same
         * context, it's priority would not exceed ELSP[0] aka last_prio.
         */
        return queue_prio(&engine->execlists) > last_prio;
}

__maybe_unused static inline bool
assert_priority_queue(const struct i915_request *prev,
                      const struct i915_request *next)
{
        /*
         * Without preemption, the prev may refer to the still active element
         * which we refuse to let go.
         *
         * Even with preemption, there are times when we think it is better not
         * to preempt and leave an ostensibly lower priority request in flight.
         */
        if (i915_request_is_active(prev))
                return true;

        return rq_prio(prev) >= rq_prio(next);
}

/*
 * The context descriptor encodes various attributes of a context,
 * including its GTT address and some flags. Because it's fairly
 * expensive to calculate, we'll just do it once and cache the result,
 * which remains valid until the context is unpinned.
 *
 * This is what a descriptor looks like, from LSB to MSB::
 *
 *      bits  0-11:    flags, GEN8_CTX_* (cached in ctx->desc_template)
 *      bits 12-31:    LRCA, GTT address of (the HWSP of) this context
 *      bits 32-52:    ctx ID, a globally unique tag (highest bit used by GuC)
 *      bits 53-54:    mbz, reserved for use by hardware
 *      bits 55-63:    group ID, currently unused and set to 0
 *
 * Starting from Gen11, the upper dword of the descriptor has a new format:
 *
 *      bits 32-36:    reserved
 *      bits 37-47:    SW context ID
 *      bits 48:53:    engine instance
 *      bit 54:        mbz, reserved for use by hardware
 *      bits 55-60:    SW counter
 *      bits 61-63:    engine class
 *
 * engine info, SW context ID and SW counter need to form a unique number
 * (Context ID) per lrc.
 */
static u64
lrc_descriptor(struct intel_context *ce, struct intel_engine_cs *engine)
{
        struct i915_gem_context *ctx = ce->gem_context;
        u64 desc;

        BUILD_BUG_ON(MAX_CONTEXT_HW_ID > (BIT(GEN8_CTX_ID_WIDTH)));
        BUILD_BUG_ON(GEN11_MAX_CONTEXT_HW_ID > (BIT(GEN11_SW_CTX_ID_WIDTH)));

        desc = INTEL_LEGACY_32B_CONTEXT;
        if (i915_vm_is_4lvl(ce->vm))
                desc = INTEL_LEGACY_64B_CONTEXT;
        desc <<= GEN8_CTX_ADDRESSING_MODE_SHIFT;

        desc |= GEN8_CTX_VALID | GEN8_CTX_PRIVILEGE;
        if (IS_GEN(engine->i915, 8))
                desc |= GEN8_CTX_L3LLC_COHERENT;

        desc |= i915_ggtt_offset(ce->state) + LRC_HEADER_PAGES * PAGE_SIZE;
                                                                /* bits 12-31 */
        /*
         * The following 32bits are copied into the OA reports (dword 2).
         * Consider updating oa_get_render_ctx_id in i915_perf.c when changing
         * anything below.
         */
        if (INTEL_GEN(engine->i915) >= 11) {
                GEM_BUG_ON(ctx->hw_id >= BIT(GEN11_SW_CTX_ID_WIDTH));
                desc |= (u64)ctx->hw_id << GEN11_SW_CTX_ID_SHIFT;
                                                                /* bits 37-47 */

                desc |= (u64)engine->instance << GEN11_ENGINE_INSTANCE_SHIFT;
                                                                /* bits 48-53 */

                /* TODO: decide what to do with SW counter (bits 55-60) */

                desc |= (u64)engine->class << GEN11_ENGINE_CLASS_SHIFT;
                                                                /* bits 61-63 */
        } else {
                GEM_BUG_ON(ctx->hw_id >= BIT(GEN8_CTX_ID_WIDTH));
                desc |= (u64)ctx->hw_id << GEN8_CTX_ID_SHIFT;   /* bits 32-52 */
        }

        return desc;
}

static void unwind_wa_tail(struct i915_request *rq)
{
        rq->tail = intel_ring_wrap(rq->ring, rq->wa_tail - WA_TAIL_BYTES);
        assert_ring_tail_valid(rq->ring, rq->tail);
}

static struct i915_request *
__unwind_incomplete_requests(struct intel_engine_cs *engine)
{
        struct i915_request *rq, *rn, *active = NULL;
        struct list_head *uninitialized_var(pl);
        int prio = I915_PRIORITY_INVALID;

        lockdep_assert_held(&engine->active.lock);

        list_for_each_entry_safe_reverse(rq, rn,
                                         &engine->active.requests,
                                         sched.link) {
                struct intel_engine_cs *owner;

                if (i915_request_completed(rq))
                        continue; /* XXX */

                __i915_request_unsubmit(rq);
                unwind_wa_tail(rq);

                /*
                 * Push the request back into the queue for later resubmission.
                 * If this request is not native to this physical engine (i.e.
                 * it came from a virtual source), push it back onto the virtual
                 * engine so that it can be moved across onto another physical
                 * engine as load dictates.
                 */
                owner = rq->hw_context->engine;
                if (likely(owner == engine)) {
                        GEM_BUG_ON(rq_prio(rq) == I915_PRIORITY_INVALID);
                        if (rq_prio(rq) != prio) {
                                prio = rq_prio(rq);
                                pl = i915_sched_lookup_priolist(engine, prio);
                        }
                        GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));

                        list_move(&rq->sched.link, pl);
                        active = rq;
                } else {
                        /*
                         * Decouple the virtual breadcrumb before moving it
                         * back to the virtual engine -- we don't want the
                         * request to complete in the background and try
                         * and cancel the breadcrumb on the virtual engine
                         * (instead of the old engine where it is linked)!
                         */
                        if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
                                     &rq->fence.flags)) {
                                spin_lock(&rq->lock);
                                i915_request_cancel_breadcrumb(rq);
                                spin_unlock(&rq->lock);
                        }
                        rq->engine = owner;
                        owner->submit_request(rq);
                        active = NULL;
                }
        }

        return active;
}

struct i915_request *
execlists_unwind_incomplete_requests(struct intel_engine_execlists *execlists)
{
        struct intel_engine_cs *engine =
                container_of(execlists, typeof(*engine), execlists);

        return __unwind_incomplete_requests(engine);
}

static inline void
execlists_context_status_change(struct i915_request *rq, unsigned long status)
{
        /*
         * Only used when GVT-g is enabled now. When GVT-g is disabled,
         * The compiler should eliminate this function as dead-code.
         */
        if (!IS_ENABLED(CONFIG_DRM_I915_GVT))
                return;

        atomic_notifier_call_chain(&rq->engine->context_status_notifier,
                                   status, rq);
}

static inline struct intel_engine_cs *
__execlists_schedule_in(struct i915_request *rq)
{
        struct intel_engine_cs * const engine = rq->engine;
        struct intel_context * const ce = rq->hw_context;

        intel_context_get(ce);

        intel_gt_pm_get(engine->gt);
        execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_IN);
        intel_engine_context_in(engine);

        return engine;
}

static inline struct i915_request *
execlists_schedule_in(struct i915_request *rq, int idx)
{
        struct intel_context * const ce = rq->hw_context;
        struct intel_engine_cs *old;

        GEM_BUG_ON(!intel_engine_pm_is_awake(rq->engine));
        trace_i915_request_in(rq, idx);

        old = READ_ONCE(ce->inflight);
        do {
                if (!old) {
                        WRITE_ONCE(ce->inflight, __execlists_schedule_in(rq));
                        break;
                }
        } while (!try_cmpxchg(&ce->inflight, &old, ptr_inc(old)));

        GEM_BUG_ON(intel_context_inflight(ce) != rq->engine);
        return i915_request_get(rq);
}

static void kick_siblings(struct i915_request *rq, struct intel_context *ce)
{
        struct virtual_engine *ve = container_of(ce, typeof(*ve), context);
        struct i915_request *next = READ_ONCE(ve->request);

        if (next && next->execution_mask & ~rq->execution_mask)
                tasklet_schedule(&ve->base.execlists.tasklet);
}

static inline void
__execlists_schedule_out(struct i915_request *rq,
                         struct intel_engine_cs * const engine)
{
        struct intel_context * const ce = rq->hw_context;

        intel_engine_context_out(engine);
        execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_OUT);
        intel_gt_pm_put(engine->gt);

        /*
         * If this is part of a virtual engine, its next request may
         * have been blocked waiting for access to the active context.
         * We have to kick all the siblings again in case we need to
         * switch (e.g. the next request is not runnable on this
         * engine). Hopefully, we will already have submitted the next
         * request before the tasklet runs and do not need to rebuild
         * each virtual tree and kick everyone again.
         */
        if (ce->engine != engine)
                kick_siblings(rq, ce);

        intel_context_put(ce);
}

static inline void
execlists_schedule_out(struct i915_request *rq)
{
        struct intel_context * const ce = rq->hw_context;
        struct intel_engine_cs *cur, *old;

        trace_i915_request_out(rq);

        old = READ_ONCE(ce->inflight);
        do
                cur = ptr_unmask_bits(old, 2) ? ptr_dec(old) : NULL;
        while (!try_cmpxchg(&ce->inflight, &old, cur));
        if (!cur)
                __execlists_schedule_out(rq, old);

        i915_request_put(rq);
}

static u64 execlists_update_context(const struct i915_request *rq)
{
        struct intel_context *ce = rq->hw_context;
        u64 desc;

        ce->lrc_reg_state[CTX_RING_TAIL + 1] =
                intel_ring_set_tail(rq->ring, rq->tail);

        /*
         * Make sure the context image is complete before we submit it to HW.
         *
         * Ostensibly, writes (including the WCB) should be flushed prior to
         * an uncached write such as our mmio register access, the empirical
         * evidence (esp. on Braswell) suggests that the WC write into memory
         * may not be visible to the HW prior to the completion of the UC
         * register write and that we may begin execution from the context
         * before its image is complete leading to invalid PD chasing.
         *
         * Furthermore, Braswell, at least, wants a full mb to be sure that
         * the writes are coherent in memory (visible to the GPU) prior to
         * execution, and not just visible to other CPUs (as is the result of
         * wmb).
         */
        mb();

        desc = ce->lrc_desc;
        ce->lrc_desc &= ~CTX_DESC_FORCE_RESTORE;

        return desc;
}

static inline void write_desc(struct intel_engine_execlists *execlists, u64 desc, u32 port)
{
        if (execlists->ctrl_reg) {
                writel(lower_32_bits(desc), execlists->submit_reg + port * 2);
                writel(upper_32_bits(desc), execlists->submit_reg + port * 2 + 1);
        } else {
                writel(upper_32_bits(desc), execlists->submit_reg);
                writel(lower_32_bits(desc), execlists->submit_reg);
        }
}

static __maybe_unused void
trace_ports(const struct intel_engine_execlists *execlists,
            const char *msg,
            struct i915_request * const *ports)
{
        const struct intel_engine_cs *engine =
                container_of(execlists, typeof(*engine), execlists);

        GEM_TRACE("%s: %s { %llx:%lld%s, %llx:%lld }\n",
                  engine->name, msg,
                  ports[0]->fence.context,
                  ports[0]->fence.seqno,
                  i915_request_completed(ports[0]) ? "!" :
                  i915_request_started(ports[0]) ? "*" :
                  "",
                  ports[1] ? ports[1]->fence.context : 0,
                  ports[1] ? ports[1]->fence.seqno : 0);
}

static __maybe_unused bool
assert_pending_valid(const struct intel_engine_execlists *execlists,
                     const char *msg)
{
        struct i915_request * const *port, *rq;
        struct intel_context *ce = NULL;

        trace_ports(execlists, msg, execlists->pending);

        if (!execlists->pending[0])
                return false;

        if (execlists->pending[execlists_num_ports(execlists)])
                return false;

        for (port = execlists->pending; (rq = *port); port++) {
                if (ce == rq->hw_context)
                        return false;

                ce = rq->hw_context;
                if (i915_request_completed(rq))
                        continue;

                if (i915_active_is_idle(&ce->active))
                        return false;

                if (!i915_vma_is_pinned(ce->state))
                        return false;
        }

        return ce;
}

static void execlists_submit_ports(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists *execlists = &engine->execlists;
        unsigned int n;

        GEM_BUG_ON(!assert_pending_valid(execlists, "submit"));

        /*
         * We can skip acquiring intel_runtime_pm_get() here as it was taken
         * on our behalf by the request (see i915_gem_mark_busy()) and it will
         * not be relinquished until the device is idle (see
         * i915_gem_idle_work_handler()). As a precaution, we make sure
         * that all ELSP are drained i.e. we have processed the CSB,
         * before allowing ourselves to idle and calling intel_runtime_pm_put().
         */
        GEM_BUG_ON(!intel_engine_pm_is_awake(engine));

        /*
         * ELSQ note: the submit queue is not cleared after being submitted
         * to the HW so we need to make sure we always clean it up. This is
         * currently ensured by the fact that we always write the same number
         * of elsq entries, keep this in mind before changing the loop below.
         */
        for (n = execlists_num_ports(execlists); n--; ) {
                struct i915_request *rq = execlists->pending[n];

                write_desc(execlists,
                           rq ? execlists_update_context(rq) : 0,
                           n);
        }

        /* we need to manually load the submit queue */
        if (execlists->ctrl_reg)
                writel(EL_CTRL_LOAD, execlists->ctrl_reg);
}

static bool ctx_single_port_submission(const struct intel_context *ce)
{
        return (IS_ENABLED(CONFIG_DRM_I915_GVT) &&
                i915_gem_context_force_single_submission(ce->gem_context));
}

static bool can_merge_ctx(const struct intel_context *prev,
                          const struct intel_context *next)
{
        if (prev != next)
                return false;

        if (ctx_single_port_submission(prev))
                return false;

        return true;
}

static bool can_merge_rq(const struct i915_request *prev,
                         const struct i915_request *next)
{
        GEM_BUG_ON(prev == next);
        GEM_BUG_ON(!assert_priority_queue(prev, next));

        /*
         * We do not submit known completed requests. Therefore if the next
         * request is already completed, we can pretend to merge it in
         * with the previous context (and we will skip updating the ELSP
         * and tracking). Thus hopefully keeping the ELSP full with active
         * contexts, despite the best efforts of preempt-to-busy to confuse
         * us.
         */
        if (i915_request_completed(next))
                return true;

        if (!can_merge_ctx(prev->hw_context, next->hw_context))
                return false;

        return true;
}

static void virtual_update_register_offsets(u32 *regs,
                                            struct intel_engine_cs *engine)
{
        u32 base = engine->mmio_base;

        /* Must match execlists_init_reg_state()! */

        regs[CTX_CONTEXT_CONTROL] =
                i915_mmio_reg_offset(RING_CONTEXT_CONTROL(base));
        regs[CTX_RING_HEAD] = i915_mmio_reg_offset(RING_HEAD(base));
        regs[CTX_RING_TAIL] = i915_mmio_reg_offset(RING_TAIL(base));
        regs[CTX_RING_BUFFER_START] = i915_mmio_reg_offset(RING_START(base));
        regs[CTX_RING_BUFFER_CONTROL] = i915_mmio_reg_offset(RING_CTL(base));

        regs[CTX_BB_HEAD_U] = i915_mmio_reg_offset(RING_BBADDR_UDW(base));
        regs[CTX_BB_HEAD_L] = i915_mmio_reg_offset(RING_BBADDR(base));
        regs[CTX_BB_STATE] = i915_mmio_reg_offset(RING_BBSTATE(base));
        regs[CTX_SECOND_BB_HEAD_U] =
                i915_mmio_reg_offset(RING_SBBADDR_UDW(base));
        regs[CTX_SECOND_BB_HEAD_L] = i915_mmio_reg_offset(RING_SBBADDR(base));
        regs[CTX_SECOND_BB_STATE] = i915_mmio_reg_offset(RING_SBBSTATE(base));

        regs[CTX_CTX_TIMESTAMP] =
                i915_mmio_reg_offset(RING_CTX_TIMESTAMP(base));
        regs[CTX_PDP3_UDW] = i915_mmio_reg_offset(GEN8_RING_PDP_UDW(base, 3));
        regs[CTX_PDP3_LDW] = i915_mmio_reg_offset(GEN8_RING_PDP_LDW(base, 3));
        regs[CTX_PDP2_UDW] = i915_mmio_reg_offset(GEN8_RING_PDP_UDW(base, 2));
        regs[CTX_PDP2_LDW] = i915_mmio_reg_offset(GEN8_RING_PDP_LDW(base, 2));
        regs[CTX_PDP1_UDW] = i915_mmio_reg_offset(GEN8_RING_PDP_UDW(base, 1));
        regs[CTX_PDP1_LDW] = i915_mmio_reg_offset(GEN8_RING_PDP_LDW(base, 1));
        regs[CTX_PDP0_UDW] = i915_mmio_reg_offset(GEN8_RING_PDP_UDW(base, 0));
        regs[CTX_PDP0_LDW] = i915_mmio_reg_offset(GEN8_RING_PDP_LDW(base, 0));

        if (engine->class == RENDER_CLASS) {
                regs[CTX_RCS_INDIRECT_CTX] =
                        i915_mmio_reg_offset(RING_INDIRECT_CTX(base));
                regs[CTX_RCS_INDIRECT_CTX_OFFSET] =
                        i915_mmio_reg_offset(RING_INDIRECT_CTX_OFFSET(base));
                regs[CTX_BB_PER_CTX_PTR] =
                        i915_mmio_reg_offset(RING_BB_PER_CTX_PTR(base));

                regs[CTX_R_PWR_CLK_STATE] =
                        i915_mmio_reg_offset(GEN8_R_PWR_CLK_STATE);
        }
}

static bool virtual_matches(const struct virtual_engine *ve,
                            const struct i915_request *rq,
                            const struct intel_engine_cs *engine)
{
        const struct intel_engine_cs *inflight;

        if (!(rq->execution_mask & engine->mask)) /* We peeked too soon! */
                return false;

        /*
         * We track when the HW has completed saving the context image
         * (i.e. when we have seen the final CS event switching out of
         * the context) and must not overwrite the context image before
         * then. This restricts us to only using the active engine
         * while the previous virtualized request is inflight (so
         * we reuse the register offsets). This is a very small
         * hystersis on the greedy seelction algorithm.
         */
        inflight = intel_context_inflight(&ve->context);
        if (inflight && inflight != engine)
                return false;

        return true;
}

static void virtual_xfer_breadcrumbs(struct virtual_engine *ve,
                                     struct intel_engine_cs *engine)
{
        struct intel_engine_cs *old = ve->siblings[0];

        /* All unattached (rq->engine == old) must already be completed */

        spin_lock(&old->breadcrumbs.irq_lock);
        if (!list_empty(&ve->context.signal_link)) {
                list_move_tail(&ve->context.signal_link,
                               &engine->breadcrumbs.signalers);
                intel_engine_queue_breadcrumbs(engine);
        }
        spin_unlock(&old->breadcrumbs.irq_lock);
}

static struct i915_request *
last_active(const struct intel_engine_execlists *execlists)
{
        struct i915_request * const *last = READ_ONCE(execlists->active);

        while (*last && i915_request_completed(*last))
                last++;

        return *last;
}

static void defer_request(struct i915_request *rq, struct list_head * const pl)
{
        LIST_HEAD(list);

        /*
         * We want to move the interrupted request to the back of
         * the round-robin list (i.e. its priority level), but
         * in doing so, we must then move all requests that were in
         * flight and were waiting for the interrupted request to
         * be run after it again.
         */
        do {
                struct i915_dependency *p;

                GEM_BUG_ON(i915_request_is_active(rq));
                list_move_tail(&rq->sched.link, pl);

                list_for_each_entry(p, &rq->sched.waiters_list, wait_link) {
                        struct i915_request *w =
                                container_of(p->waiter, typeof(*w), sched);

                        /* Leave semaphores spinning on the other engines */
                        if (w->engine != rq->engine)
                                continue;

                        /* No waiter should start before its signaler */
                        GEM_BUG_ON(i915_request_started(w) &&
                                   !i915_request_completed(rq));

                        GEM_BUG_ON(i915_request_is_active(w));
                        if (list_empty(&w->sched.link))
                                continue; /* Not yet submitted; unready */

                        if (rq_prio(w) < rq_prio(rq))
                                continue;

                        GEM_BUG_ON(rq_prio(w) > rq_prio(rq));
                        list_move_tail(&w->sched.link, &list);
                }

                rq = list_first_entry_or_null(&list, typeof(*rq), sched.link);
        } while (rq);
}

static void defer_active(struct intel_engine_cs *engine)
{
        struct i915_request *rq;

        rq = __unwind_incomplete_requests(engine);
        if (!rq)
                return;

        defer_request(rq, i915_sched_lookup_priolist(engine, rq_prio(rq)));
}

static bool
need_timeslice(struct intel_engine_cs *engine, const struct i915_request *rq)
{
        int hint;

        if (!intel_engine_has_semaphores(engine))
                return false;

        if (list_is_last(&rq->sched.link, &engine->active.requests))
                return false;

        hint = max(rq_prio(list_next_entry(rq, sched.link)),
                   engine->execlists.queue_priority_hint);

        return hint >= effective_prio(rq);
}

static int
switch_prio(struct intel_engine_cs *engine, const struct i915_request *rq)
{
        if (list_is_last(&rq->sched.link, &engine->active.requests))
                return INT_MIN;

        return rq_prio(list_next_entry(rq, sched.link));
}

static bool
enable_timeslice(const struct intel_engine_execlists *execlists)
{
        const struct i915_request *rq = *execlists->active;

        if (i915_request_completed(rq))
                return false;

        return execlists->switch_priority_hint >= effective_prio(rq);
}

static void record_preemption(struct intel_engine_execlists *execlists)
{
        (void)I915_SELFTEST_ONLY(execlists->preempt_hang.count++);
}

static void execlists_dequeue(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists * const execlists = &engine->execlists;
        struct i915_request **port = execlists->pending;
        struct i915_request ** const last_port = port + execlists->port_mask;
        struct i915_request *last;
        struct rb_node *rb;
        bool submit = false;

        /*
         * Hardware submission is through 2 ports. Conceptually each port
         * has a (RING_START, RING_HEAD, RING_TAIL) tuple. RING_START is
         * static for a context, and unique to each, so we only execute
         * requests belonging to a single context from each ring. RING_HEAD
         * is maintained by the CS in the context image, it marks the place
         * where it got up to last time, and through RING_TAIL we tell the CS
         * where we want to execute up to this time.
         *
         * In this list the requests are in order of execution. Consecutive
         * requests from the same context are adjacent in the ringbuffer. We
         * can combine these requests into a single RING_TAIL update:
         *
         *              RING_HEAD...req1...req2
         *                                    ^- RING_TAIL
         * since to execute req2 the CS must first execute req1.
         *
         * Our goal then is to point each port to the end of a consecutive
         * sequence of requests as being the most optimal (fewest wake ups
         * and context switches) submission.
         */

        for (rb = rb_first_cached(&execlists->virtual); rb; ) {
                struct virtual_engine *ve =
                        rb_entry(rb, typeof(*ve), nodes[engine->id].rb);
                struct i915_request *rq = READ_ONCE(ve->request);

                if (!rq) { /* lazily cleanup after another engine handled rq */
                        rb_erase_cached(rb, &execlists->virtual);
                        RB_CLEAR_NODE(rb);
                        rb = rb_first_cached(&execlists->virtual);
                        continue;
                }

                if (!virtual_matches(ve, rq, engine)) {
                        rb = rb_next(rb);
                        continue;
                }

                break;
        }

        /*
         * If the queue is higher priority than the last
         * request in the currently active context, submit afresh.
         * We will resubmit again afterwards in case we need to split
         * the active context to interject the preemption request,
         * i.e. we will retrigger preemption following the ack in case
         * of trouble.
         */
        last = last_active(execlists);
        if (last) {
                if (need_preempt(engine, last, rb)) {
                        GEM_TRACE("%s: preempting last=%llx:%lld, prio=%d, hint=%d\n",
                                  engine->name,
                                  last->fence.context,
                                  last->fence.seqno,
                                  last->sched.attr.priority,
                                  execlists->queue_priority_hint);
                        record_preemption(execlists);

                        /*
                         * Don't let the RING_HEAD advance past the breadcrumb
                         * as we unwind (and until we resubmit) so that we do
                         * not accidentally tell it to go backwards.
                         */
                        ring_set_paused(engine, 1);

                        /*
                         * Note that we have not stopped the GPU at this point,
                         * so we are unwinding the incomplete requests as they
                         * remain inflight and so by the time we do complete
                         * the preemption, some of the unwound requests may
                         * complete!
                         */
                        __unwind_incomplete_requests(engine);

                        /*
                         * If we need to return to the preempted context, we
                         * need to skip the lite-restore and force it to
                         * reload the RING_TAIL. Otherwise, the HW has a
                         * tendency to ignore us rewinding the TAIL to the
                         * end of an earlier request.
                         */
                        last->hw_context->lrc_desc |= CTX_DESC_FORCE_RESTORE;
                        last = NULL;
                } else if (need_timeslice(engine, last) &&
                           !timer_pending(&engine->execlists.timer)) {
                        GEM_TRACE("%s: expired last=%llx:%lld, prio=%d, hint=%d\n",
                                  engine->name,
                                  last->fence.context,
                                  last->fence.seqno,
                                  last->sched.attr.priority,
                                  execlists->queue_priority_hint);

                        ring_set_paused(engine, 1);
                        defer_active(engine);

                        /*
                         * Unlike for preemption, if we rewind and continue
                         * executing the same context as previously active,
                         * the order of execution will remain the same and
                         * the tail will only advance. We do not need to
                         * force a full context restore, as a lite-restore
                         * is sufficient to resample the monotonic TAIL.
                         *
                         * If we switch to any other context, similarly we
                         * will not rewind TAIL of current context, and
                         * normal save/restore will preserve state and allow
                         * us to later continue executing the same request.
                         */
                        last = NULL;
                } else {
                        /*
                         * Otherwise if we already have a request pending
                         * for execution after the current one, we can
                         * just wait until the next CS event before
                         * queuing more. In either case we will force a
                         * lite-restore preemption event, but if we wait
                         * we hopefully coalesce several updates into a single
                         * submission.
                         */
                        if (!list_is_last(&last->sched.link,
                                          &engine->active.requests))
                                return;

                        /*
                         * WaIdleLiteRestore:bdw,skl
                         * Apply the wa NOOPs to prevent
                         * ring:HEAD == rq:TAIL as we resubmit the
                         * request. See gen8_emit_fini_breadcrumb() for
                         * where we prepare the padding after the
                         * end of the request.
                         */
                        last->tail = last->wa_tail;
                }
        }

        while (rb) { /* XXX virtual is always taking precedence */
                struct virtual_engine *ve =
                        rb_entry(rb, typeof(*ve), nodes[engine->id].rb);
                struct i915_request *rq;

                spin_lock(&ve->base.active.lock);

                rq = ve->request;
                if (unlikely(!rq)) { /* lost the race to a sibling */
                        spin_unlock(&ve->base.active.lock);
                        rb_erase_cached(rb, &execlists->virtual);
                        RB_CLEAR_NODE(rb);
                        rb = rb_first_cached(&execlists->virtual);
                        continue;
                }

                GEM_BUG_ON(rq != ve->request);
                GEM_BUG_ON(rq->engine != &ve->base);
                GEM_BUG_ON(rq->hw_context != &ve->context);

                if (rq_prio(rq) >= queue_prio(execlists)) {
                        if (!virtual_matches(ve, rq, engine)) {
                                spin_unlock(&ve->base.active.lock);
                                rb = rb_next(rb);
                                continue;
                        }

                        if (last && !can_merge_rq(last, rq)) {
                                spin_unlock(&ve->base.active.lock);
                                return; /* leave this for another */
                        }

                        GEM_TRACE("%s: virtual rq=%llx:%lld%s, new engine? %s\n",
                                  engine->name,
                                  rq->fence.context,
                                  rq->fence.seqno,
                                  i915_request_completed(rq) ? "!" :
                                  i915_request_started(rq) ? "*" :
                                  "",
                                  yesno(engine != ve->siblings[0]));

                        ve->request = NULL;
                        ve->base.execlists.queue_priority_hint = INT_MIN;
                        rb_erase_cached(rb, &execlists->virtual);
                        RB_CLEAR_NODE(rb);

                        GEM_BUG_ON(!(rq->execution_mask & engine->mask));
                        rq->engine = engine;

                        if (engine != ve->siblings[0]) {
                                u32 *regs = ve->context.lrc_reg_state;
                                unsigned int n;

                                GEM_BUG_ON(READ_ONCE(ve->context.inflight));
                                virtual_update_register_offsets(regs, engine);

                                if (!list_empty(&ve->context.signals))
                                        virtual_xfer_breadcrumbs(ve, engine);

                                /*
                                 * Move the bound engine to the top of the list
                                 * for future execution. We then kick this
                                 * tasklet first before checking others, so that
                                 * we preferentially reuse this set of bound
                                 * registers.
                                 */
                                for (n = 1; n < ve->num_siblings; n++) {
                                        if (ve->siblings[n] == engine) {
                                                swap(ve->siblings[n],
                                                     ve->siblings[0]);
                                                break;
                                        }
                                }

                                GEM_BUG_ON(ve->siblings[0] != engine);
                        }

                        if (__i915_request_submit(rq)) {
                                submit = true;
                                last = rq;
                        }

                        /*
                         * Hmm, we have a bunch of virtual engine requests,
                         * but the first one was already completed (thanks
                         * preempt-to-busy!). Keep looking at the veng queue
                         * until we have no more relevant requests (i.e.
                         * the normal submit queue has higher priority).
                         */
                        if (!submit) {
                                spin_unlock(&ve->base.active.lock);
                                rb = rb_first_cached(&execlists->virtual);
                                continue;
                        }
                }

                spin_unlock(&ve->base.active.lock);
                break;
        }

        while ((rb = rb_first_cached(&execlists->queue))) {
                struct i915_priolist *p = to_priolist(rb);
                struct i915_request *rq, *rn;
                int i;

                priolist_for_each_request_consume(rq, rn, p, i) {
                        bool merge = true;

                        /*
                         * Can we combine this request with the current port?
                         * It has to be the same context/ringbuffer and not
                         * have any exceptions (e.g. GVT saying never to
                         * combine contexts).
                         *
                         * If we can combine the requests, we can execute both
                         * by updating the RING_TAIL to point to the end of the
                         * second request, and so we never need to tell the
                         * hardware about the first.
                         */
                        if (last && !can_merge_rq(last, rq)) {
                                /*
                                 * If we are on the second port and cannot
                                 * combine this request with the last, then we
                                 * are done.
                                 */
                                if (port == last_port)
                                        goto done;

                                /*
                                 * We must not populate both ELSP[] with the
                                 * same LRCA, i.e. we must submit 2 different
                                 * contexts if we submit 2 ELSP.
                                 */
                                if (last->hw_context == rq->hw_context)
                                        goto done;

                                /*
                                 * If GVT overrides us we only ever submit
                                 * port[0], leaving port[1] empty. Note that we
                                 * also have to be careful that we don't queue
                                 * the same context (even though a different
                                 * request) to the second port.
                                 */
                                if (ctx_single_port_submission(last->hw_context) ||
                                    ctx_single_port_submission(rq->hw_context))
                                        goto done;

                                merge = false;
                        }

                        if (__i915_request_submit(rq)) {
                                if (!merge) {
                                        *port = execlists_schedule_in(last, port - execlists->pending);
                                        port++;
                                        last = NULL;
                                }

                                GEM_BUG_ON(last &&
                                           !can_merge_ctx(last->hw_context,
                                                          rq->hw_context));

                                submit = true;
                                last = rq;
                        }
                }

                rb_erase_cached(&p->node, &execlists->queue);
                i915_priolist_free(p);
        }

done:
        /*
         * Here be a bit of magic! Or sleight-of-hand, whichever you prefer.
         *
         * We choose the priority hint such that if we add a request of greater
         * priority than this, we kick the submission tasklet to decide on
         * the right order of submitting the requests to hardware. We must
         * also be prepared to reorder requests as they are in-flight on the
         * HW. We derive the priority hint then as the first "hole" in
         * the HW submission ports and if there are no available slots,
         * the priority of the lowest executing request, i.e. last.
         *
         * When we do receive a higher priority request ready to run from the
         * user, see queue_request(), the priority hint is bumped to that
         * request triggering preemption on the next dequeue (or subsequent
         * interrupt for secondary ports).
         */
        execlists->queue_priority_hint = queue_prio(execlists);
        GEM_TRACE("%s: queue_priority_hint:%d, submit:%s\n",
                  engine->name, execlists->queue_priority_hint,
                  yesno(submit));

        if (submit) {
                *port = execlists_schedule_in(last, port - execlists->pending);
                memset(port + 1, 0, (last_port - port) * sizeof(*port));
                execlists->switch_priority_hint =
                        switch_prio(engine, *execlists->pending);
                execlists_submit_ports(engine);
        } else {
                ring_set_paused(engine, 0);
        }
}

static void
cancel_port_requests(struct intel_engine_execlists * const execlists)
{
        struct i915_request * const *port, *rq;

        for (port = execlists->pending; (rq = *port); port++)
                execlists_schedule_out(rq);
        memset(execlists->pending, 0, sizeof(execlists->pending));

        for (port = execlists->active; (rq = *port); port++)
                execlists_schedule_out(rq);
        execlists->active =
                memset(execlists->inflight, 0, sizeof(execlists->inflight));
}

static inline void
invalidate_csb_entries(const u32 *first, const u32 *last)
{
        clflush((void *)first);
        clflush((void *)last);
}

static inline bool
reset_in_progress(const struct intel_engine_execlists *execlists)
{
        return unlikely(!__tasklet_is_enabled(&execlists->tasklet));
}

enum csb_step {
        CSB_NOP,
        CSB_PROMOTE,
        CSB_PREEMPT,
        CSB_COMPLETE,
};

/*
 * Starting with Gen12, the status has a new format:
 *
 *     bit  0:     switched to new queue
 *     bit  1:     reserved
 *     bit  2:     semaphore wait mode (poll or signal), only valid when
 *                 switch detail is set to "wait on semaphore"
 *     bits 3-5:   engine class
 *     bits 6-11:  engine instance
 *     bits 12-14: reserved
 *     bits 15-25: sw context id of the lrc the GT switched to
 *     bits 26-31: sw counter of the lrc the GT switched to
 *     bits 32-35: context switch detail
 *                  - 0: ctx complete
 *                  - 1: wait on sync flip
 *                  - 2: wait on vblank
 *                  - 3: wait on scanline
 *                  - 4: wait on semaphore
 *                  - 5: context preempted (not on SEMAPHORE_WAIT or
 *                       WAIT_FOR_EVENT)
 *     bit  36:    reserved
 *     bits 37-43: wait detail (for switch detail 1 to 4)
 *     bits 44-46: reserved
 *     bits 47-57: sw context id of the lrc the GT switched away from
 *     bits 58-63: sw counter of the lrc the GT switched away from
 */
static inline enum csb_step
gen12_csb_parse(const struct intel_engine_execlists *execlists, const u32 *csb)
{
        u32 lower_dw = csb[0];
        u32 upper_dw = csb[1];
        bool ctx_to_valid = GEN12_CSB_CTX_VALID(lower_dw);
        bool ctx_away_valid = GEN12_CSB_CTX_VALID(upper_dw);
        bool new_queue = lower_dw & GEN12_CTX_STATUS_SWITCHED_TO_NEW_QUEUE;

        if (!ctx_away_valid && ctx_to_valid)
                return CSB_PROMOTE;

        /*
         * The context switch detail is not guaranteed to be 5 when a preemption
         * occurs, so we can't just check for that. The check below works for
         * all the cases we care about, including preemptions of WAIT
         * instructions and lite-restore. Preempt-to-idle via the CTRL register
         * would require some extra handling, but we don't support that.
         */
        if (new_queue && ctx_away_valid)
                return CSB_PREEMPT;

        /*
         * switch detail = 5 is covered by the case above and we do not expect a
         * context switch on an unsuccessful wait instruction since we always
         * use polling mode.
         */
        GEM_BUG_ON(GEN12_CTX_SWITCH_DETAIL(upper_dw));

        if (*execlists->active) {
                GEM_BUG_ON(!ctx_away_valid);
                return CSB_COMPLETE;
        }

        return CSB_NOP;
}

static inline enum csb_step
gen8_csb_parse(const struct intel_engine_execlists *execlists, const u32 *csb)
{
        unsigned int status = *csb;

        if (status & GEN8_CTX_STATUS_IDLE_ACTIVE)
                return CSB_PROMOTE;

        if (status & GEN8_CTX_STATUS_PREEMPTED)
                return CSB_PREEMPT;

        if (*execlists->active)
                return CSB_COMPLETE;

        return CSB_NOP;
}

static void process_csb(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists * const execlists = &engine->execlists;
        const u32 * const buf = execlists->csb_status;
        const u8 num_entries = execlists->csb_size;
        u8 head, tail;

        GEM_BUG_ON(USES_GUC_SUBMISSION(engine->i915));

        /*
         * Note that csb_write, csb_status may be either in HWSP or mmio.
         * When reading from the csb_write mmio register, we have to be
         * careful to only use the GEN8_CSB_WRITE_PTR portion, which is
         * the low 4bits. As it happens we know the next 4bits are always
         * zero and so we can simply masked off the low u8 of the register
         * and treat it identically to reading from the HWSP (without having
         * to use explicit shifting and masking, and probably bifurcating
         * the code to handle the legacy mmio read).
         */
        head = execlists->csb_head;
        tail = READ_ONCE(*execlists->csb_write);
        GEM_TRACE("%s cs-irq head=%d, tail=%d\n", engine->name, head, tail);
        if (unlikely(head == tail))
                return;

        /*
         * Hopefully paired with a wmb() in HW!
         *
         * We must complete the read of the write pointer before any reads
         * from the CSB, so that we do not see stale values. Without an rmb
         * (lfence) the HW may speculatively perform the CSB[] reads *before*
         * we perform the READ_ONCE(*csb_write).
         */
        rmb();

        do {
                enum csb_step csb_step;

                if (++head == num_entries)
                        head = 0;

                /*
                 * We are flying near dragons again.
                 *
                 * We hold a reference to the request in execlist_port[]
                 * but no more than that. We are operating in softirq
                 * context and so cannot hold any mutex or sleep. That
                 * prevents us stopping the requests we are processing
                 * in port[] from being retired simultaneously (the
                 * breadcrumb will be complete before we see the
                 * context-switch). As we only hold the reference to the
                 * request, any pointer chasing underneath the request
                 * is subject to a potential use-after-free. Thus we
                 * store all of the bookkeeping within port[] as
                 * required, and avoid using unguarded pointers beneath
                 * request itself. The same applies to the atomic
                 * status notifier.
                 */

                GEM_TRACE("%s csb[%d]: status=0x%08x:0x%08x\n",
                          engine->name, head,
                          buf[2 * head + 0], buf[2 * head + 1]);

                if (INTEL_GEN(engine->i915) >= 12)
                        csb_step = gen12_csb_parse(execlists, buf + 2 * head);
                else
                        csb_step = gen8_csb_parse(execlists, buf + 2 * head);

                switch (csb_step) {
                case CSB_PREEMPT: /* cancel old inflight, prepare for switch */
                        trace_ports(execlists, "preempted", execlists->active);

                        while (*execlists->active)
                                execlists_schedule_out(*execlists->active++);

                        /* fallthrough */
                case CSB_PROMOTE: /* switch pending to inflight */
                        GEM_BUG_ON(*execlists->active);
                        GEM_BUG_ON(!assert_pending_valid(execlists, "promote"));
                        execlists->active =
                                memcpy(execlists->inflight,
                                       execlists->pending,
                                       execlists_num_ports(execlists) *
                                       sizeof(*execlists->pending));

                        if (enable_timeslice(execlists))
                                mod_timer(&execlists->timer, jiffies + 1);

                        if (!inject_preempt_hang(execlists))
                                ring_set_paused(engine, 0);

                        WRITE_ONCE(execlists->pending[0], NULL);
                        break;

                case CSB_COMPLETE: /* port0 completed, advanced to port1 */
                        trace_ports(execlists, "completed", execlists->active);

                        /*
                         * We rely on the hardware being strongly
                         * ordered, that the breadcrumb write is
                         * coherent (visible from the CPU) before the
                         * user interrupt and CSB is processed.
                         */
                        GEM_BUG_ON(!i915_request_completed(*execlists->active) &&
                                   !reset_in_progress(execlists));
                        execlists_schedule_out(*execlists->active++);

                        GEM_BUG_ON(execlists->active - execlists->inflight >
                                   execlists_num_ports(execlists));
                        break;

                case CSB_NOP:
                        break;
                }
        } while (head != tail);

        execlists->csb_head = head;

        /*
         * Gen11 has proven to fail wrt global observation point between
         * entry and tail update, failing on the ordering and thus
         * we see an old entry in the context status buffer.
         *
         * Forcibly evict out entries for the next gpu csb update,
         * to increase the odds that we get a fresh entries with non
         * working hardware. The cost for doing so comes out mostly with
         * the wash as hardware, working or not, will need to do the
         * invalidation before.
         */
        invalidate_csb_entries(&buf[0], &buf[num_entries - 1]);
}

static void __execlists_submission_tasklet(struct intel_engine_cs *const engine)
{
        lockdep_assert_held(&engine->active.lock);
        if (!engine->execlists.pending[0]) {
                rcu_read_lock(); /* protect peeking at execlists->active */
                execlists_dequeue(engine);
                rcu_read_unlock();
        }
}

/*
 * Check the unread Context Status Buffers and manage the submission of new
 * contexts to the ELSP accordingly.
 */
static void execlists_submission_tasklet(unsigned long data)
{
        struct intel_engine_cs * const engine = (struct intel_engine_cs *)data;
        unsigned long flags;

        process_csb(engine);
        if (!READ_ONCE(engine->execlists.pending[0])) {
                spin_lock_irqsave(&engine->active.lock, flags);
                __execlists_submission_tasklet(engine);
                spin_unlock_irqrestore(&engine->active.lock, flags);
        }
}

static void execlists_submission_timer(struct timer_list *timer)
{
        struct intel_engine_cs *engine =
                from_timer(engine, timer, execlists.timer);

        /* Kick the tasklet for some interrupt coalescing and reset handling */
        tasklet_hi_schedule(&engine->execlists.tasklet);
}

static void queue_request(struct intel_engine_cs *engine,
                          struct i915_sched_node *node,
                          int prio)
{
        GEM_BUG_ON(!list_empty(&node->link));
        list_add_tail(&node->link, i915_sched_lookup_priolist(engine, prio));
}

static void __submit_queue_imm(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists * const execlists = &engine->execlists;

        if (reset_in_progress(execlists))
                return; /* defer until we restart the engine following reset */

        if (execlists->tasklet.func == execlists_submission_tasklet)
                __execlists_submission_tasklet(engine);
        else
                tasklet_hi_schedule(&execlists->tasklet);
}

static void submit_queue(struct intel_engine_cs *engine,
                         const struct i915_request *rq)
{
        struct intel_engine_execlists *execlists = &engine->execlists;

        if (rq_prio(rq) <= execlists->queue_priority_hint)
                return;

        execlists->queue_priority_hint = rq_prio(rq);
        __submit_queue_imm(engine);
}

static void execlists_submit_request(struct i915_request *request)
{
        struct intel_engine_cs *engine = request->engine;
        unsigned long flags;

        /* Will be called from irq-context when using foreign fences. */
        spin_lock_irqsave(&engine->active.lock, flags);

        queue_request(engine, &request->sched, rq_prio(request));

        GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));
        GEM_BUG_ON(list_empty(&request->sched.link));

        submit_queue(engine, request);

        spin_unlock_irqrestore(&engine->active.lock, flags);
}

static void __execlists_context_fini(struct intel_context *ce)
{
        intel_ring_put(ce->ring);
        i915_vma_put(ce->state);
}

static void execlists_context_destroy(struct kref *kref)
{
        struct intel_context *ce = container_of(kref, typeof(*ce), ref);

        GEM_BUG_ON(!i915_active_is_idle(&ce->active));
        GEM_BUG_ON(intel_context_is_pinned(ce));

        if (ce->state)
                __execlists_context_fini(ce);

        intel_context_fini(ce);
        intel_context_free(ce);
}

static void
set_redzone(void *vaddr, const struct intel_engine_cs *engine)
{
        if (!IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
                return;

        vaddr += LRC_HEADER_PAGES * PAGE_SIZE;
        vaddr += engine->context_size;

        memset(vaddr, POISON_INUSE, I915_GTT_PAGE_SIZE);
}

static void
check_redzone(const void *vaddr, const struct intel_engine_cs *engine)
{
        if (!IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
                return;

        vaddr += LRC_HEADER_PAGES * PAGE_SIZE;
        vaddr += engine->context_size;

        if (memchr_inv(vaddr, POISON_INUSE, I915_GTT_PAGE_SIZE))
                dev_err_once(engine->i915->drm.dev,
                             "%s context redzone overwritten!\n",
                             engine->name);
}

static void execlists_context_unpin(struct intel_context *ce)
{
        check_redzone((void *)ce->lrc_reg_state - LRC_STATE_PN * PAGE_SIZE,
                      ce->engine);

        i915_gem_context_unpin_hw_id(ce->gem_context);
        i915_gem_object_unpin_map(ce->state->obj);
        intel_ring_reset(ce->ring, ce->ring->tail);
}

static void
__execlists_update_reg_state(struct intel_context *ce,
                             struct intel_engine_cs *engine)
{
        struct intel_ring *ring = ce->ring;
        u32 *regs = ce->lrc_reg_state;

        GEM_BUG_ON(!intel_ring_offset_valid(ring, ring->head));
        GEM_BUG_ON(!intel_ring_offset_valid(ring, ring->tail));

        regs[CTX_RING_BUFFER_START + 1] = i915_ggtt_offset(ring->vma);
        regs[CTX_RING_HEAD + 1] = ring->head;
        regs[CTX_RING_TAIL + 1] = ring->tail;

        /* RPCS */
        if (engine->class == RENDER_CLASS) {
                regs[CTX_R_PWR_CLK_STATE + 1] =
                        intel_sseu_make_rpcs(engine->i915, &ce->sseu);

                i915_oa_init_reg_state(engine, ce, regs);
        }
}

static int
__execlists_context_pin(struct intel_context *ce,
                        struct intel_engine_cs *engine)
{
        void *vaddr;
        int ret;

        GEM_BUG_ON(!ce->state);

        ret = intel_context_active_acquire(ce);
        if (ret)
                goto err;
        GEM_BUG_ON(!i915_vma_is_pinned(ce->state));

        vaddr = i915_gem_object_pin_map(ce->state->obj,
                                        i915_coherent_map_type(engine->i915) |
                                        I915_MAP_OVERRIDE);
        if (IS_ERR(vaddr)) {
                ret = PTR_ERR(vaddr);
                goto unpin_active;
        }

        ret = i915_gem_context_pin_hw_id(ce->gem_context);
        if (ret)
                goto unpin_map;

        ce->lrc_desc = lrc_descriptor(ce, engine);
        ce->lrc_reg_state = vaddr + LRC_STATE_PN * PAGE_SIZE;
        __execlists_update_reg_state(ce, engine);

        return 0;

unpin_map:
        i915_gem_object_unpin_map(ce->state->obj);
unpin_active:
        intel_context_active_release(ce);
err:
        return ret;
}

static int execlists_context_pin(struct intel_context *ce)
{
        return __execlists_context_pin(ce, ce->engine);
}

static int execlists_context_alloc(struct intel_context *ce)
{
        return __execlists_context_alloc(ce, ce->engine);
}

static void execlists_context_reset(struct intel_context *ce)
{
        /*
         * Because we emit WA_TAIL_DWORDS there may be a disparity
         * between our bookkeeping in ce->ring->head and ce->ring->tail and
         * that stored in context. As we only write new commands from
         * ce->ring->tail onwards, everything before that is junk. If the GPU
         * starts reading from its RING_HEAD from the context, it may try to
         * execute that junk and die.
         *
         * The contexts that are stilled pinned on resume belong to the
         * kernel, and are local to each engine. All other contexts will
         * have their head/tail sanitized upon pinning before use, so they
         * will never see garbage,
         *
         * So to avoid that we reset the context images upon resume. For
         * simplicity, we just zero everything out.
         */
        intel_ring_reset(ce->ring, 0);
        __execlists_update_reg_state(ce, ce->engine);
}

static const struct intel_context_ops execlists_context_ops = {
        .alloc = execlists_context_alloc,

        .pin = execlists_context_pin,
        .unpin = execlists_context_unpin,

        .enter = intel_context_enter_engine,
        .exit = intel_context_exit_engine,

        .reset = execlists_context_reset,
        .destroy = execlists_context_destroy,
};

static int gen8_emit_init_breadcrumb(struct i915_request *rq)
{
        u32 *cs;

        GEM_BUG_ON(!rq->timeline->has_initial_breadcrumb);

        cs = intel_ring_begin(rq, 6);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        /*
         * Check if we have been preempted before we even get started.
         *
         * After this point i915_request_started() reports true, even if
         * we get preempted and so are no longer running.
         */
        *cs++ = MI_ARB_CHECK;
        *cs++ = MI_NOOP;

        *cs++ = MI_STORE_DWORD_IMM_GEN4 | MI_USE_GGTT;
        *cs++ = rq->timeline->hwsp_offset;
        *cs++ = 0;
        *cs++ = rq->fence.seqno - 1;

        intel_ring_advance(rq, cs);

        /* Record the updated position of the request's payload */
        rq->infix = intel_ring_offset(rq, cs);

        return 0;
}

static int emit_pdps(struct i915_request *rq)
{
        const struct intel_engine_cs * const engine = rq->engine;
        struct i915_ppgtt * const ppgtt = i915_vm_to_ppgtt(rq->hw_context->vm);
        int err, i;
        u32 *cs;

        GEM_BUG_ON(intel_vgpu_active(rq->i915));

        /*
         * Beware ye of the dragons, this sequence is magic!
         *
         * Small changes to this sequence can cause anything from
         * GPU hangs to forcewake errors and machine lockups!
         */

        /* Flush any residual operations from the context load */
        err = engine->emit_flush(rq, EMIT_FLUSH);
        if (err)
                return err;

        /* Magic required to prevent forcewake errors! */
        err = engine->emit_flush(rq, EMIT_INVALIDATE);
        if (err)
                return err;

        cs = intel_ring_begin(rq, 4 * GEN8_3LVL_PDPES + 2);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        /* Ensure the LRI have landed before we invalidate & continue */
        *cs++ = MI_LOAD_REGISTER_IMM(2 * GEN8_3LVL_PDPES) | MI_LRI_FORCE_POSTED;
        for (i = GEN8_3LVL_PDPES; i--; ) {
                const dma_addr_t pd_daddr = i915_page_dir_dma_addr(ppgtt, i);
                u32 base = engine->mmio_base;

                *cs++ = i915_mmio_reg_offset(GEN8_RING_PDP_UDW(base, i));
                *cs++ = upper_32_bits(pd_daddr);
                *cs++ = i915_mmio_reg_offset(GEN8_RING_PDP_LDW(base, i));
                *cs++ = lower_32_bits(pd_daddr);
        }
        *cs++ = MI_NOOP;

        intel_ring_advance(rq, cs);

        /* Be doubly sure the LRI have landed before proceeding */
        err = engine->emit_flush(rq, EMIT_FLUSH);
        if (err)
                return err;

        /* Re-invalidate the TLB for luck */
        return engine->emit_flush(rq, EMIT_INVALIDATE);
}

static int execlists_request_alloc(struct i915_request *request)
{
        int ret;

        GEM_BUG_ON(!intel_context_is_pinned(request->hw_context));

        /*
         * Flush enough space to reduce the likelihood of waiting after
         * we start building the request - in which case we will just
         * have to repeat work.
         */
        request->reserved_space += EXECLISTS_REQUEST_SIZE;

        /*
         * Note that after this point, we have committed to using
         * this request as it is being used to both track the
         * state of engine initialisation and liveness of the
         * golden renderstate above. Think twice before you try
         * to cancel/unwind this request now.
         */

        /* Unconditionally invalidate GPU caches and TLBs. */
        if (i915_vm_is_4lvl(request->hw_context->vm))
                ret = request->engine->emit_flush(request, EMIT_INVALIDATE);
        else
                ret = emit_pdps(request);
        if (ret)
                return ret;

        request->reserved_space -= EXECLISTS_REQUEST_SIZE;
        return 0;
}

/*
 * In this WA we need to set GEN8_L3SQCREG4[21:21] and reset it after
 * PIPE_CONTROL instruction. This is required for the flush to happen correctly
 * but there is a slight complication as this is applied in WA batch where the
 * values are only initialized once so we cannot take register value at the
 * beginning and reuse it further; hence we save its value to memory, upload a
 * constant value with bit21 set and then we restore it back with the saved value.
 * To simplify the WA, a constant value is formed by using the default value
 * of this register. This shouldn't be a problem because we are only modifying
 * it for a short period and this batch in non-premptible. We can ofcourse
 * use additional instructions that read the actual value of the register
 * at that time and set our bit of interest but it makes the WA complicated.
 *
 * This WA is also required for Gen9 so extracting as a function avoids
 * code duplication.
 */
static u32 *
gen8_emit_flush_coherentl3_wa(struct intel_engine_cs *engine, u32 *batch)
{
        /* NB no one else is allowed to scribble over scratch + 256! */
        *batch++ = MI_STORE_REGISTER_MEM_GEN8 | MI_SRM_LRM_GLOBAL_GTT;
        *batch++ = i915_mmio_reg_offset(GEN8_L3SQCREG4);
        *batch++ = intel_gt_scratch_offset(engine->gt,
                                           INTEL_GT_SCRATCH_FIELD_COHERENTL3_WA);
        *batch++ = 0;

        *batch++ = MI_LOAD_REGISTER_IMM(1);
        *batch++ = i915_mmio_reg_offset(GEN8_L3SQCREG4);
        *batch++ = 0x40400000 | GEN8_LQSC_FLUSH_COHERENT_LINES;

        batch = gen8_emit_pipe_control(batch,
                                       PIPE_CONTROL_CS_STALL |
                                       PIPE_CONTROL_DC_FLUSH_ENABLE,
                                       0);

        *batch++ = MI_LOAD_REGISTER_MEM_GEN8 | MI_SRM_LRM_GLOBAL_GTT;
        *batch++ = i915_mmio_reg_offset(GEN8_L3SQCREG4);
        *batch++ = intel_gt_scratch_offset(engine->gt,
                                           INTEL_GT_SCRATCH_FIELD_COHERENTL3_WA);
        *batch++ = 0;

        return batch;
}

static u32 slm_offset(struct intel_engine_cs *engine)
{
        return intel_gt_scratch_offset(engine->gt,
                                       INTEL_GT_SCRATCH_FIELD_CLEAR_SLM_WA);
}

/*
 * Typically we only have one indirect_ctx and per_ctx batch buffer which are
 * initialized at the beginning and shared across all contexts but this field
 * helps us to have multiple batches at different offsets and select them based
 * on a criteria. At the moment this batch always start at the beginning of the page
 * and at this point we don't have multiple wa_ctx batch buffers.
 *
 * The number of WA applied are not known at the beginning; we use this field
 * to return the no of DWORDS written.
 *
 * It is to be noted that this batch does not contain MI_BATCH_BUFFER_END
 * so it adds NOOPs as padding to make it cacheline aligned.
 * MI_BATCH_BUFFER_END will be added to perctx batch and both of them together
 * makes a complete batch buffer.
 */
static u32 *gen8_init_indirectctx_bb(struct intel_engine_cs *engine, u32 *batch)
{
        /* WaDisableCtxRestoreArbitration:bdw,chv */
        *batch++ = MI_ARB_ON_OFF | MI_ARB_DISABLE;

        /* WaFlushCoherentL3CacheLinesAtContextSwitch:bdw */
        if (IS_BROADWELL(engine->i915))
                batch = gen8_emit_flush_coherentl3_wa(engine, batch);

        /* WaClearSlmSpaceAtContextSwitch:bdw,chv */
        /* Actual scratch location is at 128 bytes offset */
        batch = gen8_emit_pipe_control(batch,
                                       PIPE_CONTROL_FLUSH_L3 |
                                       PIPE_CONTROL_GLOBAL_GTT_IVB |
                                       PIPE_CONTROL_CS_STALL |
                                       PIPE_CONTROL_QW_WRITE,
                                       slm_offset(engine));

        *batch++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;

        /* Pad to end of cacheline */
        while ((unsigned long)batch % CACHELINE_BYTES)
                *batch++ = MI_NOOP;

        /*
         * MI_BATCH_BUFFER_END is not required in Indirect ctx BB because
         * execution depends on the length specified in terms of cache lines
         * in the register CTX_RCS_INDIRECT_CTX
         */

        return batch;
}

struct lri {
        i915_reg_t reg;
        u32 value;
};

static u32 *emit_lri(u32 *batch, const struct lri *lri, unsigned int count)
{
        GEM_BUG_ON(!count || count > 63);

        *batch++ = MI_LOAD_REGISTER_IMM(count);
        do {
                *batch++ = i915_mmio_reg_offset(lri->reg);
                *batch++ = lri->value;
        } while (lri++, --count);
        *batch++ = MI_NOOP;

        return batch;
}

static u32 *gen9_init_indirectctx_bb(struct intel_engine_cs *engine, u32 *batch)
{
        static const struct lri lri[] = {
                /* WaDisableGatherAtSetShaderCommonSlice:skl,bxt,kbl,glk */
                {
                        COMMON_SLICE_CHICKEN2,
                        __MASKED_FIELD(GEN9_DISABLE_GATHER_AT_SET_SHADER_COMMON_SLICE,
                                       0),
                },

                /* BSpec: 11391 */
                {
                        FF_SLICE_CHICKEN,
                        __MASKED_FIELD(FF_SLICE_CHICKEN_CL_PROVOKING_VERTEX_FIX,
                                       FF_SLICE_CHICKEN_CL_PROVOKING_VERTEX_FIX),
                },

                /* BSpec: 11299 */
                {
                        _3D_CHICKEN3,
                        __MASKED_FIELD(_3D_CHICKEN_SF_PROVOKING_VERTEX_FIX,
                                       _3D_CHICKEN_SF_PROVOKING_VERTEX_FIX),
                }
        };

        *batch++ = MI_ARB_ON_OFF | MI_ARB_DISABLE;

        /* WaFlushCoherentL3CacheLinesAtContextSwitch:skl,bxt,glk */
        batch = gen8_emit_flush_coherentl3_wa(engine, batch);

        batch = emit_lri(batch, lri, ARRAY_SIZE(lri));

        /* WaMediaPoolStateCmdInWABB:bxt,glk */
        if (HAS_POOLED_EU(engine->i915)) {
                /*
                 * EU pool configuration is setup along with golden context
                 * during context initialization. This value depends on
                 * device type (2x6 or 3x6) and needs to be updated based
                 * on which subslice is disabled especially for 2x6
                 * devices, however it is safe to load default
                 * configuration of 3x6 device instead of masking off
                 * corresponding bits because HW ignores bits of a disabled
                 * subslice and drops down to appropriate config. Please
                 * see render_state_setup() in i915_gem_render_state.c for
                 * possible configurations, to avoid duplication they are
                 * not shown here again.
                 */
                *batch++ = GEN9_MEDIA_POOL_STATE;
                *batch++ = GEN9_MEDIA_POOL_ENABLE;
                *batch++ = 0x00777000;
                *batch++ = 0;
                *batch++ = 0;
                *batch++ = 0;
        }

        *batch++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;

        /* Pad to end of cacheline */
        while ((unsigned long)batch % CACHELINE_BYTES)
                *batch++ = MI_NOOP;

        return batch;
}

static u32 *
gen10_init_indirectctx_bb(struct intel_engine_cs *engine, u32 *batch)
{
        int i;

        /*
         * WaPipeControlBefore3DStateSamplePattern: cnl
         *
         * Ensure the engine is idle prior to programming a
         * 3DSTATE_SAMPLE_PATTERN during a context restore.
         */
        batch = gen8_emit_pipe_control(batch,
                                       PIPE_CONTROL_CS_STALL,
                                       0);
        /*
         * WaPipeControlBefore3DStateSamplePattern says we need 4 dwords for
         * the PIPE_CONTROL followed by 12 dwords of 0x0, so 16 dwords in
         * total. However, a PIPE_CONTROL is 6 dwords long, not 4, which is
         * confusing. Since gen8_emit_pipe_control() already advances the
         * batch by 6 dwords, we advance the other 10 here, completing a
         * cacheline. It's not clear if the workaround requires this padding
         * before other commands, or if it's just the regular padding we would
         * already have for the workaround bb, so leave it here for now.
         */
        for (i = 0; i < 10; i++)
                *batch++ = MI_NOOP;

        /* Pad to end of cacheline */
        while ((unsigned long)batch % CACHELINE_BYTES)
                *batch++ = MI_NOOP;

        return batch;
}

#define CTX_WA_BB_OBJ_SIZE (PAGE_SIZE)

static int lrc_setup_wa_ctx(struct intel_engine_cs *engine)
{
        struct drm_i915_gem_object *obj;
        struct i915_vma *vma;
        int err;

        obj = i915_gem_object_create_shmem(engine->i915, CTX_WA_BB_OBJ_SIZE);
        if (IS_ERR(obj))
                return PTR_ERR(obj);

        vma = i915_vma_instance(obj, &engine->gt->ggtt->vm, NULL);
        if (IS_ERR(vma)) {
                err = PTR_ERR(vma);
                goto err;
        }

        err = i915_vma_pin(vma, 0, 0, PIN_GLOBAL | PIN_HIGH);
        if (err)
                goto err;

        engine->wa_ctx.vma = vma;
        return 0;

err:
        i915_gem_object_put(obj);
        return err;
}

static void lrc_destroy_wa_ctx(struct intel_engine_cs *engine)
{
        i915_vma_unpin_and_release(&engine->wa_ctx.vma, 0);
}

typedef u32 *(*wa_bb_func_t)(struct intel_engine_cs *engine, u32 *batch);

static int intel_init_workaround_bb(struct intel_engine_cs *engine)
{
        struct i915_ctx_workarounds *wa_ctx = &engine->wa_ctx;
        struct i915_wa_ctx_bb *wa_bb[2] = { &wa_ctx->indirect_ctx,
                                            &wa_ctx->per_ctx };
        wa_bb_func_t wa_bb_fn[2];
        struct page *page;
        void *batch, *batch_ptr;
        unsigned int i;
        int ret;

        if (engine->class != RENDER_CLASS)
                return 0;

        switch (INTEL_GEN(engine->i915)) {
        case 12:
        case 11:
                return 0;
        case 10:
                wa_bb_fn[0] = gen10_init_indirectctx_bb;
                wa_bb_fn[1] = NULL;
                break;
        case 9:
                wa_bb_fn[0] = gen9_init_indirectctx_bb;
                wa_bb_fn[1] = NULL;
                break;
        case 8:
                wa_bb_fn[0] = gen8_init_indirectctx_bb;
                wa_bb_fn[1] = NULL;
                break;
        default:
                MISSING_CASE(INTEL_GEN(engine->i915));
                return 0;
        }

        ret = lrc_setup_wa_ctx(engine);
        if (ret) {
                DRM_DEBUG_DRIVER("Failed to setup context WA page: %d\n", ret);
                return ret;
        }

        page = i915_gem_object_get_dirty_page(wa_ctx->vma->obj, 0);
        batch = batch_ptr = kmap_atomic(page);

        /*
         * Emit the two workaround batch buffers, recording the offset from the
         * start of the workaround batch buffer object for each and their
         * respective sizes.
         */
        for (i = 0; i < ARRAY_SIZE(wa_bb_fn); i++) {
                wa_bb[i]->offset = batch_ptr - batch;
                if (GEM_DEBUG_WARN_ON(!IS_ALIGNED(wa_bb[i]->offset,
                                                  CACHELINE_BYTES))) {
                        ret = -EINVAL;
                        break;
                }
                if (wa_bb_fn[i])
                        batch_ptr = wa_bb_fn[i](engine, batch_ptr);
                wa_bb[i]->size = batch_ptr - (batch + wa_bb[i]->offset);
        }

        BUG_ON(batch_ptr - batch > CTX_WA_BB_OBJ_SIZE);

        kunmap_atomic(batch);
        if (ret)
                lrc_destroy_wa_ctx(engine);

        return ret;
}

static void enable_execlists(struct intel_engine_cs *engine)
{
        u32 mode;

        assert_forcewakes_active(engine->uncore, FORCEWAKE_ALL);

        intel_engine_set_hwsp_writemask(engine, ~0u); /* HWSTAM */

        if (INTEL_GEN(engine->i915) >= 11)
                mode = _MASKED_BIT_ENABLE(GEN11_GFX_DISABLE_LEGACY_MODE);
        else
                mode = _MASKED_BIT_ENABLE(GFX_RUN_LIST_ENABLE);
        ENGINE_WRITE_FW(engine, RING_MODE_GEN7, mode);

        ENGINE_WRITE_FW(engine, RING_MI_MODE, _MASKED_BIT_DISABLE(STOP_RING));

        ENGINE_WRITE_FW(engine,
                        RING_HWS_PGA,
                        i915_ggtt_offset(engine->status_page.vma));
        ENGINE_POSTING_READ(engine, RING_HWS_PGA);
}

static bool unexpected_starting_state(struct intel_engine_cs *engine)
{
        bool unexpected = false;

        if (ENGINE_READ_FW(engine, RING_MI_MODE) & STOP_RING) {
                DRM_DEBUG_DRIVER("STOP_RING still set in RING_MI_MODE\n");
                unexpected = true;
        }

        return unexpected;
}

static int execlists_resume(struct intel_engine_cs *engine)
{
        intel_engine_apply_workarounds(engine);
        intel_engine_apply_whitelist(engine);

        intel_mocs_init_engine(engine);

        intel_engine_reset_breadcrumbs(engine);

        if (GEM_SHOW_DEBUG() && unexpected_starting_state(engine)) {
                struct drm_printer p = drm_debug_printer(__func__);

                intel_engine_dump(engine, &p, NULL);
        }

        enable_execlists(engine);

        return 0;
}

static void execlists_reset_prepare(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists * const execlists = &engine->execlists;
        unsigned long flags;

        GEM_TRACE("%s: depth<-%d\n", engine->name,
                  atomic_read(&execlists->tasklet.count));

        /*
         * Prevent request submission to the hardware until we have
         * completed the reset in i915_gem_reset_finish(). If a request
         * is completed by one engine, it may then queue a request
         * to a second via its execlists->tasklet *just* as we are
         * calling engine->resume() and also writing the ELSP.
         * Turning off the execlists->tasklet until the reset is over
         * prevents the race.
         */
        __tasklet_disable_sync_once(&execlists->tasklet);
        GEM_BUG_ON(!reset_in_progress(execlists));

        /* And flush any current direct submission. */
        spin_lock_irqsave(&engine->active.lock, flags);
        spin_unlock_irqrestore(&engine->active.lock, flags);

        /*
         * We stop engines, otherwise we might get failed reset and a
         * dead gpu (on elk). Also as modern gpu as kbl can suffer
         * from system hang if batchbuffer is progressing when
         * the reset is issued, regardless of READY_TO_RESET ack.
         * Thus assume it is best to stop engines on all gens
         * where we have a gpu reset.
         *
         * WaKBLVECSSemaphoreWaitPoll:kbl (on ALL_ENGINES)
         *
         * FIXME: Wa for more modern gens needs to be validated
         */
        intel_engine_stop_cs(engine);
}

static void reset_csb_pointers(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists * const execlists = &engine->execlists;
        const unsigned int reset_value = execlists->csb_size - 1;

        ring_set_paused(engine, 0);

        /*
         * After a reset, the HW starts writing into CSB entry [0]. We
         * therefore have to set our HEAD pointer back one entry so that
         * the *first* entry we check is entry 0. To complicate this further,
         * as we don't wait for the first interrupt after reset, we have to
         * fake the HW write to point back to the last entry so that our
         * inline comparison of our cached head position against the last HW
         * write works even before the first interrupt.
         */
        execlists->csb_head = reset_value;
        WRITE_ONCE(*execlists->csb_write, reset_value);
        wmb(); /* Make sure this is visible to HW (paranoia?) */

        invalidate_csb_entries(&execlists->csb_status[0],
                               &execlists->csb_status[reset_value]);
}

static struct i915_request *active_request(struct i915_request *rq)
{
        const struct intel_context * const ce = rq->hw_context;
        struct i915_request *active = NULL;
        struct list_head *list;

        if (!i915_request_is_active(rq)) /* unwound, but incomplete! */
                return rq;

        list = &rq->timeline->requests;
        list_for_each_entry_from_reverse(rq, list, link) {
                if (i915_request_completed(rq))
                        break;

                if (rq->hw_context != ce)
                        break;

                active = rq;
        }

        return active;
}

static void __execlists_reset(struct intel_engine_cs *engine, bool stalled)
{
        struct intel_engine_execlists * const execlists = &engine->execlists;
        struct intel_context *ce;
        struct i915_request *rq;
        u32 *regs;

        process_csb(engine); /* drain preemption events */

        /* Following the reset, we need to reload the CSB read/write pointers */
        reset_csb_pointers(engine);

        /*
         * Save the currently executing context, even if we completed
         * its request, it was still running at the time of the
         * reset and will have been clobbered.
         */
        rq = execlists_active(execlists);
        if (!rq)
                goto unwind;

        ce = rq->hw_context;
        GEM_BUG_ON(i915_active_is_idle(&ce->active));
        GEM_BUG_ON(!i915_vma_is_pinned(ce->state));
        rq = active_request(rq);
        if (!rq) {
                ce->ring->head = ce->ring->tail;
                goto out_replay;
        }

        ce->ring->head = intel_ring_wrap(ce->ring, rq->head);

        /*
         * If this request hasn't started yet, e.g. it is waiting on a
         * semaphore, we need to avoid skipping the request or else we
         * break the signaling chain. However, if the context is corrupt
         * the request will not restart and we will be stuck with a wedged
         * device. It is quite often the case that if we issue a reset
         * while the GPU is loading the context image, that the context
         * image becomes corrupt.
         *
         * Otherwise, if we have not started yet, the request should replay
         * perfectly and we do not need to flag the result as being erroneous.
         */
        if (!i915_request_started(rq))
                goto out_replay;

        /*
         * If the request was innocent, we leave the request in the ELSP
         * and will try to replay it on restarting. The context image may
         * have been corrupted by the reset, in which case we may have
         * to service a new GPU hang, but more likely we can continue on
         * without impact.
         *
         * If the request was guilty, we presume the context is corrupt
         * and have to at least restore the RING register in the context
         * image back to the expected values to skip over the guilty request.
         */
        __i915_request_reset(rq, stalled);
        if (!stalled)
                goto out_replay;

        /*
         * We want a simple context + ring to execute the breadcrumb update.
         * We cannot rely on the context being intact across the GPU hang,
         * so clear it and rebuild just what we need for the breadcrumb.
         * All pending requests for this context will be zapped, and any
         * future request will be after userspace has had the opportunity
         * to recreate its own state.
         */
        regs = ce->lrc_reg_state;
        if (engine->pinned_default_state) {
                memcpy(regs, /* skip restoring the vanilla PPHWSP */
                       engine->pinned_default_state + LRC_STATE_PN * PAGE_SIZE,
                       engine->context_size - PAGE_SIZE);
        }
        execlists_init_reg_state(regs, ce, engine, ce->ring);

out_replay:
        GEM_TRACE("%s replay {head:%04x, tail:%04x\n",
                  engine->name, ce->ring->head, ce->ring->tail);
        intel_ring_update_space(ce->ring);
        __execlists_update_reg_state(ce, engine);

unwind:
        /* Push back any incomplete requests for replay after the reset. */
        cancel_port_requests(execlists);
        __unwind_incomplete_requests(engine);
}

static void execlists_reset(struct intel_engine_cs *engine, bool stalled)
{
        unsigned long flags;

        GEM_TRACE("%s\n", engine->name);

        spin_lock_irqsave(&engine->active.lock, flags);

        __execlists_reset(engine, stalled);

        spin_unlock_irqrestore(&engine->active.lock, flags);
}

static void nop_submission_tasklet(unsigned long data)
{
        /* The driver is wedged; don't process any more events. */
}

static void execlists_cancel_requests(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists * const execlists = &engine->execlists;
        struct i915_request *rq, *rn;
        struct rb_node *rb;
        unsigned long flags;

        GEM_TRACE("%s\n", engine->name);

        /*
         * Before we call engine->cancel_requests(), we should have exclusive
         * access to the submission state. This is arranged for us by the
         * caller disabling the interrupt generation, the tasklet and other
         * threads that may then access the same state, giving us a free hand
         * to reset state. However, we still need to let lockdep be aware that
         * we know this state may be accessed in hardirq context, so we
         * disable the irq around this manipulation and we want to keep
         * the spinlock focused on its duties and not accidentally conflate
         * coverage to the submission's irq state. (Similarly, although we
         * shouldn't need to disable irq around the manipulation of the
         * submission's irq state, we also wish to remind ourselves that
         * it is irq state.)
         */
        spin_lock_irqsave(&engine->active.lock, flags);

        __execlists_reset(engine, true);

        /* Mark all executing requests as skipped. */
        list_for_each_entry(rq, &engine->active.requests, sched.link) {
                if (!i915_request_signaled(rq))
                        dma_fence_set_error(&rq->fence, -EIO);

                i915_request_mark_complete(rq);
        }

        /* Flush the queued requests to the timeline list (for retiring). */
        while ((rb = rb_first_cached(&execlists->queue))) {
                struct i915_priolist *p = to_priolist(rb);
                int i;

                priolist_for_each_request_consume(rq, rn, p, i) {
                        __i915_request_submit(rq);
                        dma_fence_set_error(&rq->fence, -EIO);
                        i915_request_mark_complete(rq);
                }

                rb_erase_cached(&p->node, &execlists->queue);
                i915_priolist_free(p);
        }

        /* Cancel all attached virtual engines */
        while ((rb = rb_first_cached(&execlists->virtual))) {
                struct virtual_engine *ve =
                        rb_entry(rb, typeof(*ve), nodes[engine->id].rb);

                rb_erase_cached(rb, &execlists->virtual);
                RB_CLEAR_NODE(rb);

                spin_lock(&ve->base.active.lock);
                if (ve->request) {
                        ve->request->engine = engine;
                        __i915_request_submit(ve->request);
                        dma_fence_set_error(&ve->request->fence, -EIO);
                        i915_request_mark_complete(ve->request);
                        ve->base.execlists.queue_priority_hint = INT_MIN;
                        ve->request = NULL;
                }
                spin_unlock(&ve->base.active.lock);
        }

        /* Remaining _unready_ requests will be nop'ed when submitted */

        execlists->queue_priority_hint = INT_MIN;
        execlists->queue = RB_ROOT_CACHED;

        GEM_BUG_ON(__tasklet_is_enabled(&execlists->tasklet));
        execlists->tasklet.func = nop_submission_tasklet;

        spin_unlock_irqrestore(&engine->active.lock, flags);
}

static void execlists_reset_finish(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists * const execlists = &engine->execlists;

        /*
         * After a GPU reset, we may have requests to replay. Do so now while
         * we still have the forcewake to be sure that the GPU is not allowed
         * to sleep before we restart and reload a context.
         */
        GEM_BUG_ON(!reset_in_progress(execlists));
        if (!RB_EMPTY_ROOT(&execlists->queue.rb_root))
                execlists->tasklet.func(execlists->tasklet.data);

        if (__tasklet_enable(&execlists->tasklet))
                /* And kick in case we missed a new request submission. */
                tasklet_hi_schedule(&execlists->tasklet);
        GEM_TRACE("%s: depth->%d\n", engine->name,
                  atomic_read(&execlists->tasklet.count));
}

static int gen8_emit_bb_start(struct i915_request *rq,
                              u64 offset, u32 len,
                              const unsigned int flags)
{
        u32 *cs;

        cs = intel_ring_begin(rq, 4);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        /*
         * WaDisableCtxRestoreArbitration:bdw,chv
         *
         * We don't need to perform MI_ARB_ENABLE as often as we do (in
         * particular all the gen that do not need the w/a at all!), if we
         * took care to make sure that on every switch into this context
         * (both ordinary and for preemption) that arbitrartion was enabled
         * we would be fine.  However, for gen8 there is another w/a that
         * requires us to not preempt inside GPGPU execution, so we keep
         * arbitration disabled for gen8 batches. Arbitration will be
         * re-enabled before we close the request
         * (engine->emit_fini_breadcrumb).
         */
        *cs++ = MI_ARB_ON_OFF | MI_ARB_DISABLE;

        /* FIXME(BDW+): Address space and security selectors. */
        *cs++ = MI_BATCH_BUFFER_START_GEN8 |
                (flags & I915_DISPATCH_SECURE ? 0 : BIT(8));
        *cs++ = lower_32_bits(offset);
        *cs++ = upper_32_bits(offset);

        intel_ring_advance(rq, cs);

        return 0;
}

static int gen9_emit_bb_start(struct i915_request *rq,
                              u64 offset, u32 len,
                              const unsigned int flags)
{
        u32 *cs;

        cs = intel_ring_begin(rq, 6);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        *cs++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;

        *cs++ = MI_BATCH_BUFFER_START_GEN8 |
                (flags & I915_DISPATCH_SECURE ? 0 : BIT(8));
        *cs++ = lower_32_bits(offset);
        *cs++ = upper_32_bits(offset);

        *cs++ = MI_ARB_ON_OFF | MI_ARB_DISABLE;
        *cs++ = MI_NOOP;

        intel_ring_advance(rq, cs);

        return 0;
}

static void gen8_logical_ring_enable_irq(struct intel_engine_cs *engine)
{
        ENGINE_WRITE(engine, RING_IMR,
                     ~(engine->irq_enable_mask | engine->irq_keep_mask));
        ENGINE_POSTING_READ(engine, RING_IMR);
}

static void gen8_logical_ring_disable_irq(struct intel_engine_cs *engine)
{
        ENGINE_WRITE(engine, RING_IMR, ~engine->irq_keep_mask);
}

static int gen8_emit_flush(struct i915_request *request, u32 mode)
{
        u32 cmd, *cs;

        cs = intel_ring_begin(request, 4);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        cmd = MI_FLUSH_DW + 1;

        /* We always require a command barrier so that subsequent
         * commands, such as breadcrumb interrupts, are strictly ordered
         * wrt the contents of the write cache being flushed to memory
         * (and thus being coherent from the CPU).
         */
        cmd |= MI_FLUSH_DW_STORE_INDEX | MI_FLUSH_DW_OP_STOREDW;

        if (mode & EMIT_INVALIDATE) {
                cmd |= MI_INVALIDATE_TLB;
                if (request->engine->class == VIDEO_DECODE_CLASS)
                        cmd |= MI_INVALIDATE_BSD;
        }

        *cs++ = cmd;
        *cs++ = I915_GEM_HWS_SCRATCH_ADDR | MI_FLUSH_DW_USE_GTT;
        *cs++ = 0; /* upper addr */
        *cs++ = 0; /* value */
        intel_ring_advance(request, cs);

        return 0;
}

static int gen8_emit_flush_render(struct i915_request *request,
                                  u32 mode)
{
        struct intel_engine_cs *engine = request->engine;
        u32 scratch_addr =
                intel_gt_scratch_offset(engine->gt,
                                        INTEL_GT_SCRATCH_FIELD_RENDER_FLUSH);
        bool vf_flush_wa = false, dc_flush_wa = false;
        u32 *cs, flags = 0;
        int len;

        flags |= PIPE_CONTROL_CS_STALL;

        if (mode & EMIT_FLUSH) {
                flags |= PIPE_CONTROL_RENDER_TARGET_CACHE_FLUSH;
                flags |= PIPE_CONTROL_DEPTH_CACHE_FLUSH;
                flags |= PIPE_CONTROL_DC_FLUSH_ENABLE;
                flags |= PIPE_CONTROL_FLUSH_ENABLE;
        }

        if (mode & EMIT_INVALIDATE) {
                flags |= PIPE_CONTROL_TLB_INVALIDATE;
                flags |= PIPE_CONTROL_INSTRUCTION_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_TEXTURE_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_VF_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_CONST_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_STATE_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_QW_WRITE;
                flags |= PIPE_CONTROL_GLOBAL_GTT_IVB;

                /*
                 * On GEN9: before VF_CACHE_INVALIDATE we need to emit a NULL
                 * pipe control.
                 */
                if (IS_GEN(request->i915, 9))
                        vf_flush_wa = true;

                /* WaForGAMHang:kbl */
                if (IS_KBL_REVID(request->i915, 0, KBL_REVID_B0))
                        dc_flush_wa = true;
        }

        len = 6;

        if (vf_flush_wa)
                len += 6;

        if (dc_flush_wa)
                len += 12;

        cs = intel_ring_begin(request, len);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        if (vf_flush_wa)
                cs = gen8_emit_pipe_control(cs, 0, 0);

        if (dc_flush_wa)
                cs = gen8_emit_pipe_control(cs, PIPE_CONTROL_DC_FLUSH_ENABLE,
                                            0);

        cs = gen8_emit_pipe_control(cs, flags, scratch_addr);

        if (dc_flush_wa)
                cs = gen8_emit_pipe_control(cs, PIPE_CONTROL_CS_STALL, 0);

        intel_ring_advance(request, cs);

        return 0;
}

static int gen11_emit_flush_render(struct i915_request *request,
                                   u32 mode)
{
        struct intel_engine_cs *engine = request->engine;
        const u32 scratch_addr =
                intel_gt_scratch_offset(engine->gt,
                                        INTEL_GT_SCRATCH_FIELD_RENDER_FLUSH);

        if (mode & EMIT_FLUSH) {
                u32 *cs;
                u32 flags = 0;

                flags |= PIPE_CONTROL_CS_STALL;

                flags |= PIPE_CONTROL_TILE_CACHE_FLUSH;
                flags |= PIPE_CONTROL_RENDER_TARGET_CACHE_FLUSH;
                flags |= PIPE_CONTROL_DEPTH_CACHE_FLUSH;
                flags |= PIPE_CONTROL_DC_FLUSH_ENABLE;
                flags |= PIPE_CONTROL_FLUSH_ENABLE;
                flags |= PIPE_CONTROL_QW_WRITE;
                flags |= PIPE_CONTROL_GLOBAL_GTT_IVB;

                cs = intel_ring_begin(request, 6);
                if (IS_ERR(cs))
                        return PTR_ERR(cs);

                cs = gen8_emit_pipe_control(cs, flags, scratch_addr);
                intel_ring_advance(request, cs);
        }

        if (mode & EMIT_INVALIDATE) {
                u32 *cs;
                u32 flags = 0;

                flags |= PIPE_CONTROL_CS_STALL;

                flags |= PIPE_CONTROL_COMMAND_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_TLB_INVALIDATE;
                flags |= PIPE_CONTROL_INSTRUCTION_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_TEXTURE_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_VF_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_CONST_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_STATE_CACHE_INVALIDATE;
                flags |= PIPE_CONTROL_QW_WRITE;
                flags |= PIPE_CONTROL_GLOBAL_GTT_IVB;

                cs = intel_ring_begin(request, 6);
                if (IS_ERR(cs))
                        return PTR_ERR(cs);

                cs = gen8_emit_pipe_control(cs, flags, scratch_addr);
                intel_ring_advance(request, cs);
        }

        return 0;
}

/*
 * Reserve space for 2 NOOPs at the end of each request to be
 * used as a workaround for not being allowed to do lite
 * restore with HEAD==TAIL (WaIdleLiteRestore).
 */
static u32 *gen8_emit_wa_tail(struct i915_request *request, u32 *cs)
{
        /* Ensure there's always at least one preemption point per-request. */
        *cs++ = MI_ARB_CHECK;
        *cs++ = MI_NOOP;
        request->wa_tail = intel_ring_offset(request, cs);

        return cs;
}

static u32 *emit_preempt_busywait(struct i915_request *request, u32 *cs)
{
        *cs++ = MI_SEMAPHORE_WAIT |
                MI_SEMAPHORE_GLOBAL_GTT |
                MI_SEMAPHORE_POLL |
                MI_SEMAPHORE_SAD_EQ_SDD;
        *cs++ = 0;
        *cs++ = intel_hws_preempt_address(request->engine);
        *cs++ = 0;

        return cs;
}

static __always_inline u32*
gen8_emit_fini_breadcrumb_footer(struct i915_request *request,
                                 u32 *cs)
{
        *cs++ = MI_USER_INTERRUPT;

        *cs++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;
        if (intel_engine_has_semaphores(request->engine))
                cs = emit_preempt_busywait(request, cs);

        request->tail = intel_ring_offset(request, cs);
        assert_ring_tail_valid(request->ring, request->tail);

        return gen8_emit_wa_tail(request, cs);
}

static u32 *gen8_emit_fini_breadcrumb(struct i915_request *request, u32 *cs)
{
        cs = gen8_emit_ggtt_write(cs,
                                  request->fence.seqno,
                                  request->timeline->hwsp_offset,
                                  0);

        return gen8_emit_fini_breadcrumb_footer(request, cs);
}

static u32 *gen8_emit_fini_breadcrumb_rcs(struct i915_request *request, u32 *cs)
{
        cs = gen8_emit_ggtt_write_rcs(cs,
                                      request->fence.seqno,
                                      request->timeline->hwsp_offset,
                                      PIPE_CONTROL_RENDER_TARGET_CACHE_FLUSH |
                                      PIPE_CONTROL_DEPTH_CACHE_FLUSH |
                                      PIPE_CONTROL_DC_FLUSH_ENABLE);

        /* XXX flush+write+CS_STALL all in one upsets gem_concurrent_blt:kbl */
        cs = gen8_emit_pipe_control(cs,
                                    PIPE_CONTROL_FLUSH_ENABLE |
                                    PIPE_CONTROL_CS_STALL,
                                    0);

        return gen8_emit_fini_breadcrumb_footer(request, cs);
}

static u32 *gen11_emit_fini_breadcrumb_rcs(struct i915_request *request,
                                           u32 *cs)
{
        cs = gen8_emit_ggtt_write_rcs(cs,
                                      request->fence.seqno,
                                      request->timeline->hwsp_offset,
                                      PIPE_CONTROL_CS_STALL |
                                      PIPE_CONTROL_TILE_CACHE_FLUSH |
                                      PIPE_CONTROL_RENDER_TARGET_CACHE_FLUSH |
                                      PIPE_CONTROL_DEPTH_CACHE_FLUSH |
                                      PIPE_CONTROL_DC_FLUSH_ENABLE |
                                      PIPE_CONTROL_FLUSH_ENABLE);

        return gen8_emit_fini_breadcrumb_footer(request, cs);
}

static void execlists_park(struct intel_engine_cs *engine)
{
        del_timer(&engine->execlists.timer);
}

void intel_execlists_set_default_submission(struct intel_engine_cs *engine)
{
        engine->submit_request = execlists_submit_request;
        engine->cancel_requests = execlists_cancel_requests;
        engine->schedule = i915_schedule;
        engine->execlists.tasklet.func = execlists_submission_tasklet;

        engine->reset.prepare = execlists_reset_prepare;
        engine->reset.reset = execlists_reset;
        engine->reset.finish = execlists_reset_finish;

        engine->park = execlists_park;
        engine->unpark = NULL;

        engine->flags |= I915_ENGINE_SUPPORTS_STATS;
        if (!intel_vgpu_active(engine->i915)) {
                engine->flags |= I915_ENGINE_HAS_SEMAPHORES;
                if (HAS_LOGICAL_RING_PREEMPTION(engine->i915))
                        engine->flags |= I915_ENGINE_HAS_PREEMPTION;
        }
}

static void execlists_destroy(struct intel_engine_cs *engine)
{
        intel_engine_cleanup_common(engine);
        lrc_destroy_wa_ctx(engine);
        kfree(engine);
}

static void
logical_ring_default_vfuncs(struct intel_engine_cs *engine)
{
        /* Default vfuncs which can be overriden by each engine. */

        engine->destroy = execlists_destroy;
        engine->resume = execlists_resume;

        engine->reset.prepare = execlists_reset_prepare;
        engine->reset.reset = execlists_reset;
        engine->reset.finish = execlists_reset_finish;

        engine->cops = &execlists_context_ops;
        engine->request_alloc = execlists_request_alloc;

        engine->emit_flush = gen8_emit_flush;
        engine->emit_init_breadcrumb = gen8_emit_init_breadcrumb;
        engine->emit_fini_breadcrumb = gen8_emit_fini_breadcrumb;

        engine->set_default_submission = intel_execlists_set_default_submission;

        if (INTEL_GEN(engine->i915) < 11) {
                engine->irq_enable = gen8_logical_ring_enable_irq;
                engine->irq_disable = gen8_logical_ring_disable_irq;
        } else {
                /*
                 * TODO: On Gen11 interrupt masks need to be clear
                 * to allow C6 entry. Keep interrupts enabled at
                 * and take the hit of generating extra interrupts
                 * until a more refined solution exists.
                 */
        }
        if (IS_GEN(engine->i915, 8))
                engine->emit_bb_start = gen8_emit_bb_start;
        else
                engine->emit_bb_start = gen9_emit_bb_start;
}

static inline void
logical_ring_default_irqs(struct intel_engine_cs *engine)
{
        unsigned int shift = 0;

        if (INTEL_GEN(engine->i915) < 11) {
                const u8 irq_shifts[] = {
                        [RCS0]  = GEN8_RCS_IRQ_SHIFT,
                        [BCS0]  = GEN8_BCS_IRQ_SHIFT,
                        [VCS0]  = GEN8_VCS0_IRQ_SHIFT,
                        [VCS1]  = GEN8_VCS1_IRQ_SHIFT,
                        [VECS0] = GEN8_VECS_IRQ_SHIFT,
                };

                shift = irq_shifts[engine->id];
        }

        engine->irq_enable_mask = GT_RENDER_USER_INTERRUPT << shift;
        engine->irq_keep_mask = GT_CONTEXT_SWITCH_INTERRUPT << shift;
}

static void rcs_submission_override(struct intel_engine_cs *engine)
{
        switch (INTEL_GEN(engine->i915)) {
        case 12:
        case 11:
                engine->emit_flush = gen11_emit_flush_render;
                engine->emit_fini_breadcrumb = gen11_emit_fini_breadcrumb_rcs;
                break;
        default:
                engine->emit_flush = gen8_emit_flush_render;
                engine->emit_fini_breadcrumb = gen8_emit_fini_breadcrumb_rcs;
                break;
        }
}

int intel_execlists_submission_setup(struct intel_engine_cs *engine)
{
        tasklet_init(&engine->execlists.tasklet,
                     execlists_submission_tasklet, (unsigned long)engine);
        timer_setup(&engine->execlists.timer, execlists_submission_timer, 0);

        logical_ring_default_vfuncs(engine);
        logical_ring_default_irqs(engine);

        if (engine->class == RENDER_CLASS)
                rcs_submission_override(engine);

        return 0;
}

int intel_execlists_submission_init(struct intel_engine_cs *engine)
{
        struct intel_engine_execlists * const execlists = &engine->execlists;
        struct drm_i915_private *i915 = engine->i915;
        struct intel_uncore *uncore = engine->uncore;
        u32 base = engine->mmio_base;
        int ret;

        ret = intel_engine_init_common(engine);
        if (ret)
                return ret;

        if (intel_init_workaround_bb(engine))
                /*
                 * We continue even if we fail to initialize WA batch
                 * because we only expect rare glitches but nothing
                 * critical to prevent us from using GPU
                 */
                DRM_ERROR("WA batch buffer initialization failed\n");

        if (HAS_LOGICAL_RING_ELSQ(i915)) {
                execlists->submit_reg = uncore->regs +
                        i915_mmio_reg_offset(RING_EXECLIST_SQ_CONTENTS(base));
                execlists->ctrl_reg = uncore->regs +
                        i915_mmio_reg_offset(RING_EXECLIST_CONTROL(base));
        } else {
                execlists->submit_reg = uncore->regs +
                        i915_mmio_reg_offset(RING_ELSP(base));
        }

        execlists->csb_status =
                &engine->status_page.addr[I915_HWS_CSB_BUF0_INDEX];

        execlists->csb_write =
                &engine->status_page.addr[intel_hws_csb_write_index(i915)];

        if (INTEL_GEN(i915) < 11)
                execlists->csb_size = GEN8_CSB_ENTRIES;
        else
                execlists->csb_size = GEN11_CSB_ENTRIES;

        reset_csb_pointers(engine);

        return 0;
}

static u32 intel_lr_indirect_ctx_offset(struct intel_engine_cs *engine)
{
        u32 indirect_ctx_offset;

        switch (INTEL_GEN(engine->i915)) {
        default:
                MISSING_CASE(INTEL_GEN(engine->i915));
                /* fall through */
        case 12:
                indirect_ctx_offset =
                        GEN12_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT;
                break;
        case 11:
                indirect_ctx_offset =
                        GEN11_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT;
                break;
        case 10:
                indirect_ctx_offset =
                        GEN10_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT;
                break;
        case 9:
                indirect_ctx_offset =
                        GEN9_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT;
                break;
        case 8:
                indirect_ctx_offset =
                        GEN8_CTX_RCS_INDIRECT_CTX_OFFSET_DEFAULT;
                break;
        }

        return indirect_ctx_offset;
}

static void execlists_init_reg_state(u32 *regs,
                                     struct intel_context *ce,
                                     struct intel_engine_cs *engine,
                                     struct intel_ring *ring)
{
        struct i915_ppgtt *ppgtt = i915_vm_to_ppgtt(ce->vm);
        bool rcs = engine->class == RENDER_CLASS;
        u32 base = engine->mmio_base;

        /*
         * A context is actually a big batch buffer with several
         * MI_LOAD_REGISTER_IMM commands followed by (reg, value) pairs. The
         * values we are setting here are only for the first context restore:
         * on a subsequent save, the GPU will recreate this batchbuffer with new
         * values (including all the missing MI_LOAD_REGISTER_IMM commands that
         * we are not initializing here).
         *
         * Must keep consistent with virtual_update_register_offsets().
         */
        regs[CTX_LRI_HEADER_0] = MI_LOAD_REGISTER_IMM(rcs ? 14 : 11) |
                                 MI_LRI_FORCE_POSTED;

        CTX_REG(regs, CTX_CONTEXT_CONTROL, RING_CONTEXT_CONTROL(base),
                _MASKED_BIT_DISABLE(CTX_CTRL_ENGINE_CTX_RESTORE_INHIBIT) |
                _MASKED_BIT_ENABLE(CTX_CTRL_INHIBIT_SYN_CTX_SWITCH));
        if (INTEL_GEN(engine->i915) < 11) {
                regs[CTX_CONTEXT_CONTROL + 1] |=
                        _MASKED_BIT_DISABLE(CTX_CTRL_ENGINE_CTX_SAVE_INHIBIT |
                                            CTX_CTRL_RS_CTX_ENABLE);
        }
        CTX_REG(regs, CTX_RING_HEAD, RING_HEAD(base), 0);
        CTX_REG(regs, CTX_RING_TAIL, RING_TAIL(base), 0);
        CTX_REG(regs, CTX_RING_BUFFER_START, RING_START(base), 0);
        CTX_REG(regs, CTX_RING_BUFFER_CONTROL, RING_CTL(base),
                RING_CTL_SIZE(ring->size) | RING_VALID);
        CTX_REG(regs, CTX_BB_HEAD_U, RING_BBADDR_UDW(base), 0);
        CTX_REG(regs, CTX_BB_HEAD_L, RING_BBADDR(base), 0);
        CTX_REG(regs, CTX_BB_STATE, RING_BBSTATE(base), RING_BB_PPGTT);
        CTX_REG(regs, CTX_SECOND_BB_HEAD_U, RING_SBBADDR_UDW(base), 0);
        CTX_REG(regs, CTX_SECOND_BB_HEAD_L, RING_SBBADDR(base), 0);
        CTX_REG(regs, CTX_SECOND_BB_STATE, RING_SBBSTATE(base), 0);
        if (rcs) {
                struct i915_ctx_workarounds *wa_ctx = &engine->wa_ctx;

                CTX_REG(regs, CTX_RCS_INDIRECT_CTX, RING_INDIRECT_CTX(base), 0);
                CTX_REG(regs, CTX_RCS_INDIRECT_CTX_OFFSET,
                        RING_INDIRECT_CTX_OFFSET(base), 0);
                if (wa_ctx->indirect_ctx.size) {
                        u32 ggtt_offset = i915_ggtt_offset(wa_ctx->vma);

                        regs[CTX_RCS_INDIRECT_CTX + 1] =
                                (ggtt_offset + wa_ctx->indirect_ctx.offset) |
                                (wa_ctx->indirect_ctx.size / CACHELINE_BYTES);

                        regs[CTX_RCS_INDIRECT_CTX_OFFSET + 1] =
                                intel_lr_indirect_ctx_offset(engine) << 6;
                }

                CTX_REG(regs, CTX_BB_PER_CTX_PTR, RING_BB_PER_CTX_PTR(base), 0);
                if (wa_ctx->per_ctx.size) {
                        u32 ggtt_offset = i915_ggtt_offset(wa_ctx->vma);

                        regs[CTX_BB_PER_CTX_PTR + 1] =
                                (ggtt_offset + wa_ctx->per_ctx.offset) | 0x01;
                }
        }

        regs[CTX_LRI_HEADER_1] = MI_LOAD_REGISTER_IMM(9) | MI_LRI_FORCE_POSTED;

        CTX_REG(regs, CTX_CTX_TIMESTAMP, RING_CTX_TIMESTAMP(base), 0);
        /* PDP values well be assigned later if needed */
        CTX_REG(regs, CTX_PDP3_UDW, GEN8_RING_PDP_UDW(base, 3), 0);
        CTX_REG(regs, CTX_PDP3_LDW, GEN8_RING_PDP_LDW(base, 3), 0);
        CTX_REG(regs, CTX_PDP2_UDW, GEN8_RING_PDP_UDW(base, 2), 0);
        CTX_REG(regs, CTX_PDP2_LDW, GEN8_RING_PDP_LDW(base, 2), 0);
        CTX_REG(regs, CTX_PDP1_UDW, GEN8_RING_PDP_UDW(base, 1), 0);
        CTX_REG(regs, CTX_PDP1_LDW, GEN8_RING_PDP_LDW(base, 1), 0);
        CTX_REG(regs, CTX_PDP0_UDW, GEN8_RING_PDP_UDW(base, 0), 0);
        CTX_REG(regs, CTX_PDP0_LDW, GEN8_RING_PDP_LDW(base, 0), 0);

        if (i915_vm_is_4lvl(&ppgtt->vm)) {
                /* 64b PPGTT (48bit canonical)
                 * PDP0_DESCRIPTOR contains the base address to PML4 and
                 * other PDP Descriptors are ignored.
                 */
                ASSIGN_CTX_PML4(ppgtt, regs);
        } else {
                ASSIGN_CTX_PDP(ppgtt, regs, 3);
                ASSIGN_CTX_PDP(ppgtt, regs, 2);
                ASSIGN_CTX_PDP(ppgtt, regs, 1);
                ASSIGN_CTX_PDP(ppgtt, regs, 0);
        }

        if (rcs) {
                regs[CTX_LRI_HEADER_2] = MI_LOAD_REGISTER_IMM(1);
                CTX_REG(regs, CTX_R_PWR_CLK_STATE, GEN8_R_PWR_CLK_STATE, 0);
        }

        regs[CTX_END] = MI_BATCH_BUFFER_END;
        if (INTEL_GEN(engine->i915) >= 10)
                regs[CTX_END] |= BIT(0);
}

static int
populate_lr_context(struct intel_context *ce,
                    struct drm_i915_gem_object *ctx_obj,
                    struct intel_engine_cs *engine,
                    struct intel_ring *ring)
{
        void *vaddr;
        u32 *regs;
        int ret;

        vaddr = i915_gem_object_pin_map(ctx_obj, I915_MAP_WB);
        if (IS_ERR(vaddr)) {
                ret = PTR_ERR(vaddr);
                DRM_DEBUG_DRIVER("Could not map object pages! (%d)\n", ret);
                return ret;
        }

        set_redzone(vaddr, engine);

        if (engine->default_state) {
                /*
                 * We only want to copy over the template context state;
                 * skipping over the headers reserved for GuC communication,
                 * leaving those as zero.
                 */
                const unsigned long start = LRC_HEADER_PAGES * PAGE_SIZE;
                void *defaults;

                defaults = i915_gem_object_pin_map(engine->default_state,
                                                   I915_MAP_WB);
                if (IS_ERR(defaults)) {
                        ret = PTR_ERR(defaults);
                        goto err_unpin_ctx;
                }

                memcpy(vaddr + start, defaults + start, engine->context_size);
                i915_gem_object_unpin_map(engine->default_state);
        }

        /* The second page of the context object contains some fields which must
         * be set up prior to the first execution. */
        regs = vaddr + LRC_STATE_PN * PAGE_SIZE;
        execlists_init_reg_state(regs, ce, engine, ring);
        if (!engine->default_state)
                regs[CTX_CONTEXT_CONTROL + 1] |=
                        _MASKED_BIT_ENABLE(CTX_CTRL_ENGINE_CTX_RESTORE_INHIBIT);

        ret = 0;
err_unpin_ctx:
        __i915_gem_object_flush_map(ctx_obj,
                                    LRC_HEADER_PAGES * PAGE_SIZE,
                                    engine->context_size);
        i915_gem_object_unpin_map(ctx_obj);
        return ret;
}

static int __execlists_context_alloc(struct intel_context *ce,
                                     struct intel_engine_cs *engine)
{
        struct drm_i915_gem_object *ctx_obj;
        struct intel_ring *ring;
        struct i915_vma *vma;
        u32 context_size;
        int ret;

        GEM_BUG_ON(ce->state);
        context_size = round_up(engine->context_size, I915_GTT_PAGE_SIZE);

        /*
         * Before the actual start of the context image, we insert a few pages
         * for our own use and for sharing with the GuC.
         */
        context_size += LRC_HEADER_PAGES * PAGE_SIZE;
        if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
                context_size += I915_GTT_PAGE_SIZE; /* for redzone */

        ctx_obj = i915_gem_object_create_shmem(engine->i915, context_size);
        if (IS_ERR(ctx_obj))
                return PTR_ERR(ctx_obj);

        vma = i915_vma_instance(ctx_obj, &engine->gt->ggtt->vm, NULL);
        if (IS_ERR(vma)) {
                ret = PTR_ERR(vma);
                goto error_deref_obj;
        }

        if (!ce->timeline) {
                struct intel_timeline *tl;

                tl = intel_timeline_create(engine->gt, NULL);
                if (IS_ERR(tl)) {
                        ret = PTR_ERR(tl);
                        goto error_deref_obj;
                }

                ce->timeline = tl;
        }

        ring = intel_engine_create_ring(engine, (unsigned long)ce->ring);
        if (IS_ERR(ring)) {
                ret = PTR_ERR(ring);
                goto error_deref_obj;
        }

        ret = populate_lr_context(ce, ctx_obj, engine, ring);
        if (ret) {
                DRM_DEBUG_DRIVER("Failed to populate LRC: %d\n", ret);
                goto error_ring_free;
        }

        ce->ring = ring;
        ce->state = vma;

        return 0;

error_ring_free:
        intel_ring_put(ring);
error_deref_obj:
        i915_gem_object_put(ctx_obj);
        return ret;
}

static struct list_head *virtual_queue(struct virtual_engine *ve)
{
        return &ve->base.execlists.default_priolist.requests[0];
}

static void virtual_context_destroy(struct kref *kref)
{
        struct virtual_engine *ve =
                container_of(kref, typeof(*ve), context.ref);
        unsigned int n;

        GEM_BUG_ON(!list_empty(virtual_queue(ve)));
        GEM_BUG_ON(ve->request);
        GEM_BUG_ON(ve->context.inflight);

        for (n = 0; n < ve->num_siblings; n++) {
                struct intel_engine_cs *sibling = ve->siblings[n];
                struct rb_node *node = &ve->nodes[sibling->id].rb;

                if (RB_EMPTY_NODE(node))
                        continue;

                spin_lock_irq(&sibling->active.lock);

                /* Detachment is lazily performed in the execlists tasklet */
                if (!RB_EMPTY_NODE(node))
                        rb_erase_cached(node, &sibling->execlists.virtual);

                spin_unlock_irq(&sibling->active.lock);
        }
        GEM_BUG_ON(__tasklet_is_scheduled(&ve->base.execlists.tasklet));

        if (ve->context.state)
                __execlists_context_fini(&ve->context);
        intel_context_fini(&ve->context);

        kfree(ve->bonds);
        kfree(ve);
}

static void virtual_engine_initial_hint(struct virtual_engine *ve)
{
        int swp;

        /*
         * Pick a random sibling on starting to help spread the load around.
         *
         * New contexts are typically created with exactly the same order
         * of siblings, and often started in batches. Due to the way we iterate
         * the array of sibling when submitting requests, sibling[0] is
         * prioritised for dequeuing. If we make sure that sibling[0] is fairly
         * randomised across the system, we also help spread the load by the
         * first engine we inspect being different each time.
         *
         * NB This does not force us to execute on this engine, it will just
         * typically be the first we inspect for submission.
         */
        swp = prandom_u32_max(ve->num_siblings);
        if (!swp)
                return;

        swap(ve->siblings[swp], ve->siblings[0]);
        virtual_update_register_offsets(ve->context.lrc_reg_state,
                                        ve->siblings[0]);
}

static int virtual_context_pin(struct intel_context *ce)
{
        struct virtual_engine *ve = container_of(ce, typeof(*ve), context);
        int err;

        /* Note: we must use a real engine class for setting up reg state */
        err = __execlists_context_pin(ce, ve->siblings[0]);
        if (err)
                return err;

        virtual_engine_initial_hint(ve);
        return 0;
}

static void virtual_context_enter(struct intel_context *ce)
{
        struct virtual_engine *ve = container_of(ce, typeof(*ve), context);
        unsigned int n;

        for (n = 0; n < ve->num_siblings; n++)
                intel_engine_pm_get(ve->siblings[n]);

        intel_timeline_enter(ce->timeline);
}

static void virtual_context_exit(struct intel_context *ce)
{
        struct virtual_engine *ve = container_of(ce, typeof(*ve), context);
        unsigned int n;

        intel_timeline_exit(ce->timeline);

        for (n = 0; n < ve->num_siblings; n++)
                intel_engine_pm_put(ve->siblings[n]);
}

static const struct intel_context_ops virtual_context_ops = {
        .pin = virtual_context_pin,
        .unpin = execlists_context_unpin,

        .enter = virtual_context_enter,
        .exit = virtual_context_exit,

        .destroy = virtual_context_destroy,
};

static intel_engine_mask_t virtual_submission_mask(struct virtual_engine *ve)
{
        struct i915_request *rq;
        intel_engine_mask_t mask;

        rq = READ_ONCE(ve->request);
        if (!rq)
                return 0;

        /* The rq is ready for submission; rq->execution_mask is now stable. */
        mask = rq->execution_mask;
        if (unlikely(!mask)) {
                /* Invalid selection, submit to a random engine in error */
                i915_request_skip(rq, -ENODEV);
                mask = ve->siblings[0]->mask;
        }

        GEM_TRACE("%s: rq=%llx:%lld, mask=%x, prio=%d\n",
                  ve->base.name,
                  rq->fence.context, rq->fence.seqno,
                  mask, ve->base.execlists.queue_priority_hint);

        return mask;
}

static void virtual_submission_tasklet(unsigned long data)
{
        struct virtual_engine * const ve = (struct virtual_engine *)data;
        const int prio = ve->base.execlists.queue_priority_hint;
        intel_engine_mask_t mask;
        unsigned int n;

        rcu_read_lock();
        mask = virtual_submission_mask(ve);
        rcu_read_unlock();
        if (unlikely(!mask))
                return;

        local_irq_disable();
        for (n = 0; READ_ONCE(ve->request) && n < ve->num_siblings; n++) {
                struct intel_engine_cs *sibling = ve->siblings[n];
                struct ve_node * const node = &ve->nodes[sibling->id];
                struct rb_node **parent, *rb;
                bool first;

                if (unlikely(!(mask & sibling->mask))) {
                        if (!RB_EMPTY_NODE(&node->rb)) {
                                spin_lock(&sibling->active.lock);
                                rb_erase_cached(&node->rb,
                                                &sibling->execlists.virtual);
                                RB_CLEAR_NODE(&node->rb);
                                spin_unlock(&sibling->active.lock);
                        }
                        continue;
                }

                spin_lock(&sibling->active.lock);

                if (!RB_EMPTY_NODE(&node->rb)) {
                        /*
                         * Cheat and avoid rebalancing the tree if we can
                         * reuse this node in situ.
                         */
                        first = rb_first_cached(&sibling->execlists.virtual) ==
                                &node->rb;
                        if (prio == node->prio || (prio > node->prio && first))
                                goto submit_engine;

                        rb_erase_cached(&node->rb, &sibling->execlists.virtual);
                }

                rb = NULL;
                first = true;
                parent = &sibling->execlists.virtual.rb_root.rb_node;
                while (*parent) {
                        struct ve_node *other;

                        rb = *parent;
                        other = rb_entry(rb, typeof(*other), rb);
                        if (prio > other->prio) {
                                parent = &rb->rb_left;
                        } else {
                                parent = &rb->rb_right;
                                first = false;
                        }
                }

                rb_link_node(&node->rb, rb, parent);
                rb_insert_color_cached(&node->rb,
                                       &sibling->execlists.virtual,
                                       first);

submit_engine:
                GEM_BUG_ON(RB_EMPTY_NODE(&node->rb));
                node->prio = prio;
                if (first && prio > sibling->execlists.queue_priority_hint) {
                        sibling->execlists.queue_priority_hint = prio;
                        tasklet_hi_schedule(&sibling->execlists.tasklet);
                }

                spin_unlock(&sibling->active.lock);
        }
        local_irq_enable();
}

static void virtual_submit_request(struct i915_request *rq)
{
        struct virtual_engine *ve = to_virtual_engine(rq->engine);

        GEM_TRACE("%s: rq=%llx:%lld\n",
                  ve->base.name,
                  rq->fence.context,
                  rq->fence.seqno);

        GEM_BUG_ON(ve->base.submit_request != virtual_submit_request);

        GEM_BUG_ON(ve->request);
        GEM_BUG_ON(!list_empty(virtual_queue(ve)));

        ve->base.execlists.queue_priority_hint = rq_prio(rq);
        WRITE_ONCE(ve->request, rq);

        list_move_tail(&rq->sched.link, virtual_queue(ve));

        tasklet_schedule(&ve->base.execlists.tasklet);
}

static struct ve_bond *
virtual_find_bond(struct virtual_engine *ve,
                  const struct intel_engine_cs *master)
{
        int i;

        for (i = 0; i < ve->num_bonds; i++) {
                if (ve->bonds[i].master == master)
                        return &ve->bonds[i];
        }

        return NULL;
}

static void
virtual_bond_execute(struct i915_request *rq, struct dma_fence *signal)
{
        struct virtual_engine *ve = to_virtual_engine(rq->engine);
        intel_engine_mask_t allowed, exec;
        struct ve_bond *bond;

        allowed = ~to_request(signal)->engine->mask;

        bond = virtual_find_bond(ve, to_request(signal)->engine);
        if (bond)
                allowed &= bond->sibling_mask;

        /* Restrict the bonded request to run on only the available engines */
        exec = READ_ONCE(rq->execution_mask);
        while (!try_cmpxchg(&rq->execution_mask, &exec, exec & allowed))
                ;

        /* Prevent the master from being re-run on the bonded engines */
        to_request(signal)->execution_mask &= ~allowed;
}

struct intel_context *
intel_execlists_create_virtual(struct i915_gem_context *ctx,
                               struct intel_engine_cs **siblings,
                               unsigned int count)
{
        struct virtual_engine *ve;
        unsigned int n;
        int err;

        if (count == 0)
                return ERR_PTR(-EINVAL);

        if (count == 1)
                return intel_context_create(ctx, siblings[0]);

        ve = kzalloc(struct_size(ve, siblings, count), GFP_KERNEL);
        if (!ve)
                return ERR_PTR(-ENOMEM);

        ve->base.i915 = ctx->i915;
        ve->base.gt = siblings[0]->gt;
        ve->base.id = -1;
        ve->base.class = OTHER_CLASS;
        ve->base.uabi_class = I915_ENGINE_CLASS_INVALID;
        ve->base.instance = I915_ENGINE_CLASS_INVALID_VIRTUAL;

        /*
         * The decision on whether to submit a request using semaphores
         * depends on the saturated state of the engine. We only compute
         * this during HW submission of the request, and we need for this
         * state to be globally applied to all requests being submitted
         * to this engine. Virtual engines encompass more than one physical
         * engine and so we cannot accurately tell in advance if one of those
         * engines is already saturated and so cannot afford to use a semaphore
         * and be pessimized in priority for doing so -- if we are the only
         * context using semaphores after all other clients have stopped, we
         * will be starved on the saturated system. Such a global switch for
         * semaphores is less than ideal, but alas is the current compromise.
         */
        ve->base.saturated = ALL_ENGINES;

        snprintf(ve->base.name, sizeof(ve->base.name), "virtual");

        intel_engine_init_active(&ve->base, ENGINE_VIRTUAL);

        intel_engine_init_execlists(&ve->base);

        ve->base.cops = &virtual_context_ops;
        ve->base.request_alloc = execlists_request_alloc;

        ve->base.schedule = i915_schedule;
        ve->base.submit_request = virtual_submit_request;
        ve->base.bond_execute = virtual_bond_execute;

        INIT_LIST_HEAD(virtual_queue(ve));
        ve->base.execlists.queue_priority_hint = INT_MIN;
        tasklet_init(&ve->base.execlists.tasklet,
                     virtual_submission_tasklet,
                     (unsigned long)ve);

        intel_context_init(&ve->context, ctx, &ve->base);

        for (n = 0; n < count; n++) {
                struct intel_engine_cs *sibling = siblings[n];

                GEM_BUG_ON(!is_power_of_2(sibling->mask));
                if (sibling->mask & ve->base.mask) {
                        DRM_DEBUG("duplicate %s entry in load balancer\n",
                                  sibling->name);
                        err = -EINVAL;
                        goto err_put;
                }

                /*
                 * The virtual engine implementation is tightly coupled to
                 * the execlists backend -- we push out request directly
                 * into a tree inside each physical engine. We could support
                 * layering if we handle cloning of the requests and
                 * submitting a copy into each backend.
                 */
                if (sibling->execlists.tasklet.func !=
                    execlists_submission_tasklet) {
                        err = -ENODEV;
                        goto err_put;
                }

                GEM_BUG_ON(RB_EMPTY_NODE(&ve->nodes[sibling->id].rb));
                RB_CLEAR_NODE(&ve->nodes[sibling->id].rb);

                ve->siblings[ve->num_siblings++] = sibling;
                ve->base.mask |= sibling->mask;

                /*
                 * All physical engines must be compatible for their emission
                 * functions (as we build the instructions during request
                 * construction and do not alter them before submission
                 * on the physical engine). We use the engine class as a guide
                 * here, although that could be refined.
                 */
                if (ve->base.class != OTHER_CLASS) {
                        if (ve->base.class != sibling->class) {
                                DRM_DEBUG("invalid mixing of engine class, sibling %d, already %d\n",
                                          sibling->class, ve->base.class);
                                err = -EINVAL;
                                goto err_put;
                        }
                        continue;
                }

                ve->base.class = sibling->class;
                ve->base.uabi_class = sibling->uabi_class;
                snprintf(ve->base.name, sizeof(ve->base.name),
                         "v%dx%d", ve->base.class, count);
                ve->base.context_size = sibling->context_size;

                ve->base.emit_bb_start = sibling->emit_bb_start;
                ve->base.emit_flush = sibling->emit_flush;
                ve->base.emit_init_breadcrumb = sibling->emit_init_breadcrumb;
                ve->base.emit_fini_breadcrumb = sibling->emit_fini_breadcrumb;
                ve->base.emit_fini_breadcrumb_dw =
                        sibling->emit_fini_breadcrumb_dw;

                ve->base.flags = sibling->flags;
        }

        ve->base.flags |= I915_ENGINE_IS_VIRTUAL;

        err = __execlists_context_alloc(&ve->context, siblings[0]);
        if (err)
                goto err_put;

        __set_bit(CONTEXT_ALLOC_BIT, &ve->context.flags);

        return &ve->context;

err_put:
        intel_context_put(&ve->context);
        return ERR_PTR(err);
}

struct intel_context *
intel_execlists_clone_virtual(struct i915_gem_context *ctx,
                              struct intel_engine_cs *src)
{
        struct virtual_engine *se = to_virtual_engine(src);
        struct intel_context *dst;

        dst = intel_execlists_create_virtual(ctx,
                                             se->siblings,
                                             se->num_siblings);
        if (IS_ERR(dst))
                return dst;

        if (se->num_bonds) {
                struct virtual_engine *de = to_virtual_engine(dst->engine);

                de->bonds = kmemdup(se->bonds,
                                    sizeof(*se->bonds) * se->num_bonds,
                                    GFP_KERNEL);
                if (!de->bonds) {
                        intel_context_put(dst);
                        return ERR_PTR(-ENOMEM);
                }

                de->num_bonds = se->num_bonds;
        }

        return dst;
}

int intel_virtual_engine_attach_bond(struct intel_engine_cs *engine,
                                     const struct intel_engine_cs *master,
                                     const struct intel_engine_cs *sibling)
{
        struct virtual_engine *ve = to_virtual_engine(engine);
        struct ve_bond *bond;
        int n;

        /* Sanity check the sibling is part of the virtual engine */
        for (n = 0; n < ve->num_siblings; n++)
                if (sibling == ve->siblings[n])
                        break;
        if (n == ve->num_siblings)
                return -EINVAL;

        bond = virtual_find_bond(ve, master);
        if (bond) {
                bond->sibling_mask |= sibling->mask;
                return 0;
        }

        bond = krealloc(ve->bonds,
                        sizeof(*bond) * (ve->num_bonds + 1),
                        GFP_KERNEL);
        if (!bond)
                return -ENOMEM;

        bond[ve->num_bonds].master = master;
        bond[ve->num_bonds].sibling_mask = sibling->mask;

        ve->bonds = bond;
        ve->num_bonds++;

        return 0;
}

void intel_execlists_show_requests(struct intel_engine_cs *engine,
                                   struct drm_printer *m,
                                   void (*show_request)(struct drm_printer *m,
                                                        struct i915_request *rq,
                                                        const char *prefix),
                                   unsigned int max)
{
        const struct intel_engine_execlists *execlists = &engine->execlists;
        struct i915_request *rq, *last;
        unsigned long flags;
        unsigned int count;
        struct rb_node *rb;

        spin_lock_irqsave(&engine->active.lock, flags);

        last = NULL;
        count = 0;
        list_for_each_entry(rq, &engine->active.requests, sched.link) {
                if (count++ < max - 1)
                        show_request(m, rq, "\t\tE ");
                else
                        last = rq;
        }
        if (last) {
                if (count > max) {
                        drm_printf(m,
                                   "\t\t...skipping %d executing requests...\n",
                                   count - max);
                }
                show_request(m, last, "\t\tE ");
        }

        last = NULL;
        count = 0;
        if (execlists->queue_priority_hint != INT_MIN)
                drm_printf(m, "\t\tQueue priority hint: %d\n",
                           execlists->queue_priority_hint);
        for (rb = rb_first_cached(&execlists->queue); rb; rb = rb_next(rb)) {
                struct i915_priolist *p = rb_entry(rb, typeof(*p), node);
                int i;

                priolist_for_each_request(rq, p, i) {
                        if (count++ < max - 1)
                                show_request(m, rq, "\t\tQ ");
                        else
                                last = rq;
                }
        }
        if (last) {
                if (count > max) {
                        drm_printf(m,
                                   "\t\t...skipping %d queued requests...\n",
                                   count - max);
                }
                show_request(m, last, "\t\tQ ");
        }

        last = NULL;
        count = 0;
        for (rb = rb_first_cached(&execlists->virtual); rb; rb = rb_next(rb)) {
                struct virtual_engine *ve =
                        rb_entry(rb, typeof(*ve), nodes[engine->id].rb);
                struct i915_request *rq = READ_ONCE(ve->request);

                if (rq) {
                        if (count++ < max - 1)
                                show_request(m, rq, "\t\tV ");
                        else
                                last = rq;
                }
        }
        if (last) {
                if (count > max) {
                        drm_printf(m,
                                   "\t\t...skipping %d virtual requests...\n",
                                   count - max);
                }
                show_request(m, last, "\t\tV ");
        }

        spin_unlock_irqrestore(&engine->active.lock, flags);
}

void intel_lr_context_reset(struct intel_engine_cs *engine,
                            struct intel_context *ce,
                            u32 head,
                            bool scrub)
{
        /*
         * We want a simple context + ring to execute the breadcrumb update.
         * We cannot rely on the context being intact across the GPU hang,
         * so clear it and rebuild just what we need for the breadcrumb.
         * All pending requests for this context will be zapped, and any
         * future request will be after userspace has had the opportunity
         * to recreate its own state.
         */
        if (scrub) {
                u32 *regs = ce->lrc_reg_state;

                if (engine->pinned_default_state) {
                        memcpy(regs, /* skip restoring the vanilla PPHWSP */
                               engine->pinned_default_state + LRC_STATE_PN * PAGE_SIZE,
                               engine->context_size - PAGE_SIZE);
                }
                execlists_init_reg_state(regs, ce, engine, ce->ring);
        }

        /* Rerun the request; its payload has been neutered (if guilty). */
        ce->ring->head = head;
        intel_ring_update_space(ce->ring);

        __execlists_update_reg_state(ce, engine);
}

#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftest_lrc.c"
#endif