[RFC PATCH v3 10/58] perf: Add generic exclude_guest support

[Mingwei Zhang <mizhang@xxxxxxxxxx>]

From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>

Only KVM knows the exact time when a guest is entering/exiting. Expose
two interfaces to KVM to switch the ownership of the PMU resources.

Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Tested-by: Yongwei Ma <yongwei.ma@xxxxxxxxx>
Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
---
 include/linux/perf_event.h |  4 +++
 kernel/events/core.c       | 54 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 81a5f8399cb8..75773f9890cc 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1738,6 +1738,8 @@ extern int perf_event_period(struct perf_event *event, u64 value);
 extern u64 perf_event_pause(struct perf_event *event, bool reset);
 int perf_get_mediated_pmu(void);
 void perf_put_mediated_pmu(void);
+void perf_guest_enter(void);
+void perf_guest_exit(void);
 #else /* !CONFIG_PERF_EVENTS: */
 static inline void *
 perf_aux_output_begin(struct perf_output_handle *handle,
@@ -1831,6 +1833,8 @@ static inline int perf_get_mediated_pmu(void)
 }
 
 static inline void perf_put_mediated_pmu(void)			{ }
+static inline void perf_guest_enter(void)			{ }
+static inline void perf_guest_exit(void)			{ }
 #endif
 
 #if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 57648736e43e..57ff737b922b 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5941,6 +5941,60 @@ void perf_put_mediated_pmu(void)
 }
 EXPORT_SYMBOL_GPL(perf_put_mediated_pmu);
 
+/* When entering a guest, schedule out all exclude_guest events. */
+void perf_guest_enter(void)
+{
+	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
+
+	lockdep_assert_irqs_disabled();
+
+	perf_ctx_lock(cpuctx, cpuctx->task_ctx);
+
+	if (WARN_ON_ONCE(__this_cpu_read(perf_in_guest)))
+		goto unlock;
+
+	perf_ctx_disable(&cpuctx->ctx, EVENT_GUEST);
+	ctx_sched_out(&cpuctx->ctx, EVENT_GUEST);
+	perf_ctx_enable(&cpuctx->ctx, EVENT_GUEST);
+	if (cpuctx->task_ctx) {
+		perf_ctx_disable(cpuctx->task_ctx, EVENT_GUEST);
+		task_ctx_sched_out(cpuctx->task_ctx, EVENT_GUEST);
+		perf_ctx_enable(cpuctx->task_ctx, EVENT_GUEST);
+	}
+
+	__this_cpu_write(perf_in_guest, true);
+
+unlock:
+	perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
+}
+EXPORT_SYMBOL_GPL(perf_guest_enter);
+
+void perf_guest_exit(void)
+{
+	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
+
+	lockdep_assert_irqs_disabled();
+
+	perf_ctx_lock(cpuctx, cpuctx->task_ctx);
+
+	if (WARN_ON_ONCE(!__this_cpu_read(perf_in_guest)))
+		goto unlock;
+
+	perf_ctx_disable(&cpuctx->ctx, EVENT_GUEST);
+	ctx_sched_in(&cpuctx->ctx, EVENT_GUEST);
+	perf_ctx_enable(&cpuctx->ctx, EVENT_GUEST);
+	if (cpuctx->task_ctx) {
+		perf_ctx_disable(cpuctx->task_ctx, EVENT_GUEST);
+		ctx_sched_in(cpuctx->task_ctx, EVENT_GUEST);
+		perf_ctx_enable(cpuctx->task_ctx, EVENT_GUEST);
+	}
+
+	__this_cpu_write(perf_in_guest, false);
+unlock:
+	perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
+}
+EXPORT_SYMBOL_GPL(perf_guest_exit);
+
 /*
  * Holding the top-level event's child_mutex means that any
  * descendant process that has inherited this event will block
-- 
2.46.0.rc1.232.g9752f9e123-goog