#include <linux/clocksource.h>
#include <linux/sched_clock.h>
#include <linux/mm.h>
+#include <linux/cpuhotplug.h>
#include <clocksource/hyperv_timer.h>
#include <asm/hyperv-tlfs.h>
#include <asm/mshyperv.h>
* mechanism is used when running on older versions of Hyper-V
* that don't support Direct Mode. While Hyper-V provides
* four stimer's per CPU, Linux uses only stimer0.
+ *
+ * Because Direct Mode does not require processing a VMbus
+ * message, stimer interrupts can be enabled earlier in the
+ * process of booting a CPU, and consistent with when timer
+ * interrupts are enabled for other clocksource drivers.
+ * However, for legacy versions of Hyper-V when Direct Mode
+ * is not enabled, setting up stimer interrupts must be
+ * delayed until VMbus is initialized and can process the
+ * interrupt message.
*/
static bool direct_mode_enabled;
/*
* hv_stimer_init - Per-cpu initialization of the clockevent
*/
-void hv_stimer_init(unsigned int cpu)
+static int hv_stimer_init(unsigned int cpu)
{
struct clock_event_device *ce;
- /*
- * Synthetic timers are always available except on old versions of
- * Hyper-V on x86. In that case, just return as Linux will use a
- * clocksource based on emulated PIT or LAPIC timer hardware.
- */
- if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
- return;
+ if (!hv_clock_event)
+ return 0;
ce = per_cpu_ptr(hv_clock_event, cpu);
ce->name = "Hyper-V clockevent";
HV_CLOCK_HZ,
HV_MIN_DELTA_TICKS,
HV_MAX_MAX_DELTA_TICKS);
+ return 0;
}
-EXPORT_SYMBOL_GPL(hv_stimer_init);
/*
* hv_stimer_cleanup - Per-cpu cleanup of the clockevent
*/
-void hv_stimer_cleanup(unsigned int cpu)
+int hv_stimer_cleanup(unsigned int cpu)
{
struct clock_event_device *ce;
- /* Turn off clockevent device */
- if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
- ce = per_cpu_ptr(hv_clock_event, cpu);
+ if (!hv_clock_event)
+ return 0;
+
+ /*
+ * In the legacy case where Direct Mode is not enabled
+ * (which can only be on x86/64), stimer cleanup happens
+ * relatively early in the CPU offlining process. We
+ * must unbind the stimer-based clockevent device so
+ * that the LAPIC timer can take over until clockevents
+ * are no longer needed in the offlining process. Note
+ * that clockevents_unbind_device() eventually calls
+ * hv_ce_shutdown().
+ *
+ * The unbind should not be done when Direct Mode is
+ * enabled because we may be on an architecture where
+ * there are no other clockevent devices to fallback to.
+ */
+ ce = per_cpu_ptr(hv_clock_event, cpu);
+ if (direct_mode_enabled)
hv_ce_shutdown(ce);
- }
+ else
+ clockevents_unbind_device(ce, cpu);
+
+ return 0;
}
EXPORT_SYMBOL_GPL(hv_stimer_cleanup);
/* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
-int hv_stimer_alloc(int sint)
+int hv_stimer_alloc(void)
{
- int ret;
+ int ret = 0;
+
+ /*
+ * Synthetic timers are always available except on old versions of
+ * Hyper-V on x86. In that case, return as error as Linux will use a
+ * clockevent based on emulated LAPIC timer hardware.
+ */
+ if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
+ return -EINVAL;
hv_clock_event = alloc_percpu(struct clock_event_device);
if (!hv_clock_event)
if (direct_mode_enabled) {
ret = hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
hv_stimer0_isr);
- if (ret) {
- free_percpu(hv_clock_event);
- hv_clock_event = NULL;
- return ret;
- }
+ if (ret)
+ goto free_percpu;
+
+ /*
+ * Since we are in Direct Mode, stimer initialization
+ * can be done now with a CPUHP value in the same range
+ * as other clockevent devices.
+ */
+ ret = cpuhp_setup_state(CPUHP_AP_HYPERV_TIMER_STARTING,
+ "clockevents/hyperv/stimer:starting",
+ hv_stimer_init, hv_stimer_cleanup);
+ if (ret < 0)
+ goto free_stimer0_irq;
}
+ return ret;
- stimer0_message_sint = sint;
- return 0;
+free_stimer0_irq:
+ hv_remove_stimer0_irq(stimer0_irq);
+ stimer0_irq = 0;
+free_percpu:
+ free_percpu(hv_clock_event);
+ hv_clock_event = NULL;
+ return ret;
}
EXPORT_SYMBOL_GPL(hv_stimer_alloc);
+/*
+ * hv_stimer_legacy_init -- Called from the VMbus driver to handle
+ * the case when Direct Mode is not enabled, and the stimer
+ * must be initialized late in the CPU onlining process.
+ *
+ */
+void hv_stimer_legacy_init(unsigned int cpu, int sint)
+{
+ if (direct_mode_enabled)
+ return;
+
+ /*
+ * This function gets called by each vCPU, so setting the
+ * global stimer_message_sint value each time is conceptually
+ * not ideal, but the value passed in is always the same and
+ * it avoids introducing yet another interface into this
+ * clocksource driver just to set the sint in the legacy case.
+ */
+ stimer0_message_sint = sint;
+ (void)hv_stimer_init(cpu);
+}
+EXPORT_SYMBOL_GPL(hv_stimer_legacy_init);
+
+/*
+ * hv_stimer_legacy_cleanup -- Called from the VMbus driver to
+ * handle the case when Direct Mode is not enabled, and the
+ * stimer must be cleaned up early in the CPU offlining
+ * process.
+ */
+void hv_stimer_legacy_cleanup(unsigned int cpu)
+{
+ if (direct_mode_enabled)
+ return;
+ (void)hv_stimer_cleanup(cpu);
+}
+EXPORT_SYMBOL_GPL(hv_stimer_legacy_cleanup);
+
+
/* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
void hv_stimer_free(void)
{
- if (direct_mode_enabled && (stimer0_irq != 0)) {
+ if (!hv_clock_event)
+ return;
+
+ if (direct_mode_enabled) {
+ cpuhp_remove_state(CPUHP_AP_HYPERV_TIMER_STARTING);
hv_remove_stimer0_irq(stimer0_irq);
stimer0_irq = 0;
}
void hv_stimer_global_cleanup(void)
{
int cpu;
- struct clock_event_device *ce;
- if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
- for_each_present_cpu(cpu) {
- ce = per_cpu_ptr(hv_clock_event, cpu);
- clockevents_unbind_device(ce, cpu);
- }
+ /*
+ * hv_stime_legacy_cleanup() will stop the stimer if Direct
+ * Mode is not enabled, and fallback to the LAPIC timer.
+ */
+ for_each_present_cpu(cpu) {
+ hv_stimer_legacy_cleanup(cpu);
}
+
+ /*
+ * If Direct Mode is enabled, the cpuhp teardown callback
+ * (hv_stimer_cleanup) will be run on all CPUs to stop the
+ * stimers.
+ */
hv_stimer_free();
}
EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
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