--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Hyper-V stub IOMMU driver.
+ *
+ * Copyright (C) 2019, Microsoft, Inc.
+ *
+ * Author : Lan Tianyu <Tianyu.Lan@microsoft.com>
+ */
+
+#include <linux/types.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/iommu.h>
+#include <linux/module.h>
+
+#include <asm/apic.h>
+#include <asm/cpu.h>
+#include <asm/hw_irq.h>
+#include <asm/io_apic.h>
+#include <asm/irq_remapping.h>
+#include <asm/hypervisor.h>
+
+#include "irq_remapping.h"
+
+#ifdef CONFIG_IRQ_REMAP
+
+/*
+ * According 82093AA IO-APIC spec , IO APIC has a 24-entry Interrupt
+ * Redirection Table. Hyper-V exposes one single IO-APIC and so define
+ * 24 IO APIC remmapping entries.
+ */
+#define IOAPIC_REMAPPING_ENTRY 24
+
+static cpumask_t ioapic_max_cpumask = { CPU_BITS_NONE };
+static struct irq_domain *ioapic_ir_domain;
+
+static int hyperv_ir_set_affinity(struct irq_data *data,
+ const struct cpumask *mask, bool force)
+{
+ struct irq_data *parent = data->parent_data;
+ struct irq_cfg *cfg = irqd_cfg(data);
+ struct IO_APIC_route_entry *entry;
+ int ret;
+
+ /* Return error If new irq affinity is out of ioapic_max_cpumask. */
+ if (!cpumask_subset(mask, &ioapic_max_cpumask))
+ return -EINVAL;
+
+ ret = parent->chip->irq_set_affinity(parent, mask, force);
+ if (ret < 0 || ret == IRQ_SET_MASK_OK_DONE)
+ return ret;
+
+ entry = data->chip_data;
+ entry->dest = cfg->dest_apicid;
+ entry->vector = cfg->vector;
+ send_cleanup_vector(cfg);
+
+ return 0;
+}
+
+static struct irq_chip hyperv_ir_chip = {
+ .name = "HYPERV-IR",
+ .irq_ack = apic_ack_irq,
+ .irq_set_affinity = hyperv_ir_set_affinity,
+};
+
+static int hyperv_irq_remapping_alloc(struct irq_domain *domain,
+ unsigned int virq, unsigned int nr_irqs,
+ void *arg)
+{
+ struct irq_alloc_info *info = arg;
+ struct irq_data *irq_data;
+ struct irq_desc *desc;
+ int ret = 0;
+
+ if (!info || info->type != X86_IRQ_ALLOC_TYPE_IOAPIC || nr_irqs > 1)
+ return -EINVAL;
+
+ ret = irq_domain_alloc_irqs_parent(domain, virq, nr_irqs, arg);
+ if (ret < 0)
+ return ret;
+
+ irq_data = irq_domain_get_irq_data(domain, virq);
+ if (!irq_data) {
+ irq_domain_free_irqs_common(domain, virq, nr_irqs);
+ return -EINVAL;
+ }
+
+ irq_data->chip = &hyperv_ir_chip;
+
+ /*
+ * If there is interrupt remapping function of IOMMU, setting irq
+ * affinity only needs to change IRTE of IOMMU. But Hyper-V doesn't
+ * support interrupt remapping function, setting irq affinity of IO-APIC
+ * interrupts still needs to change IO-APIC registers. But ioapic_
+ * configure_entry() will ignore value of cfg->vector and cfg->
+ * dest_apicid when IO-APIC's parent irq domain is not the vector
+ * domain.(See ioapic_configure_entry()) In order to setting vector
+ * and dest_apicid to IO-APIC register, IO-APIC entry pointer is saved
+ * in the chip_data and hyperv_irq_remapping_activate()/hyperv_ir_set_
+ * affinity() set vector and dest_apicid directly into IO-APIC entry.
+ */
+ irq_data->chip_data = info->ioapic_entry;
+
+ /*
+ * Hypver-V IO APIC irq affinity should be in the scope of
+ * ioapic_max_cpumask because no irq remapping support.
+ */
+ desc = irq_data_to_desc(irq_data);
+ cpumask_copy(desc->irq_common_data.affinity, &ioapic_max_cpumask);
+
+ return 0;
+}
+
+static void hyperv_irq_remapping_free(struct irq_domain *domain,
+ unsigned int virq, unsigned int nr_irqs)
+{
+ irq_domain_free_irqs_common(domain, virq, nr_irqs);
+}
+
+static int hyperv_irq_remapping_activate(struct irq_domain *domain,
+ struct irq_data *irq_data, bool reserve)
+{
+ struct irq_cfg *cfg = irqd_cfg(irq_data);
+ struct IO_APIC_route_entry *entry = irq_data->chip_data;
+
+ entry->dest = cfg->dest_apicid;
+ entry->vector = cfg->vector;
+
+ return 0;
+}
+
+static struct irq_domain_ops hyperv_ir_domain_ops = {
+ .alloc = hyperv_irq_remapping_alloc,
+ .free = hyperv_irq_remapping_free,
+ .activate = hyperv_irq_remapping_activate,
+};
+
+static int __init hyperv_prepare_irq_remapping(void)
+{
+ struct fwnode_handle *fn;
+ int i;
+
+ if (!hypervisor_is_type(X86_HYPER_MS_HYPERV) ||
+ !x2apic_supported())
+ return -ENODEV;
+
+ fn = irq_domain_alloc_named_id_fwnode("HYPERV-IR", 0);
+ if (!fn)
+ return -ENOMEM;
+
+ ioapic_ir_domain =
+ irq_domain_create_hierarchy(arch_get_ir_parent_domain(),
+ 0, IOAPIC_REMAPPING_ENTRY, fn,
+ &hyperv_ir_domain_ops, NULL);
+
+ irq_domain_free_fwnode(fn);
+
+ /*
+ * Hyper-V doesn't provide irq remapping function for
+ * IO-APIC and so IO-APIC only accepts 8-bit APIC ID.
+ * Cpu's APIC ID is read from ACPI MADT table and APIC IDs
+ * in the MADT table on Hyper-v are sorted monotonic increasingly.
+ * APIC ID reflects cpu topology. There maybe some APIC ID
+ * gaps when cpu number in a socket is not power of two. Prepare
+ * max cpu affinity for IOAPIC irqs. Scan cpu 0-255 and set cpu
+ * into ioapic_max_cpumask if its APIC ID is less than 256.
+ */
+ for (i = min_t(unsigned int, num_possible_cpus() - 1, 255); i >= 0; i--)
+ if (cpu_physical_id(i) < 256)
+ cpumask_set_cpu(i, &ioapic_max_cpumask);
+
+ return 0;
+}
+
+static int __init hyperv_enable_irq_remapping(void)
+{
+ return IRQ_REMAP_X2APIC_MODE;
+}
+
+static struct irq_domain *hyperv_get_ir_irq_domain(struct irq_alloc_info *info)
+{
+ if (info->type == X86_IRQ_ALLOC_TYPE_IOAPIC)
+ return ioapic_ir_domain;
+ else
+ return NULL;
+}
+
+struct irq_remap_ops hyperv_irq_remap_ops = {
+ .prepare = hyperv_prepare_irq_remapping,
+ .enable = hyperv_enable_irq_remapping,
+ .get_ir_irq_domain = hyperv_get_ir_irq_domain,
+};
+
+#endif
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