Install Intel specific PMU task context synchronization adapter and
extend optimized context switch path with PMU specific task context
synchronization to fix LBR callstack virtualization on context switches.
Signed-off-by: Alexey Budankov <alexey.budan...@linux.intel.com>
---
arch/x86/events/intel/core.c | 7 +++++++
kernel/events/core.c | 13 ++++++++++++-
2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index bbf6588d47ee..dc64b16e6b71 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3820,6 +3820,12 @@ static void intel_pmu_sched_task(struct
perf_event_context *ctx,
intel_pmu_lbr_sched_task(ctx, sched_in);
}
+static void intel_pmu_swap_task_ctx(struct perf_event_context *prev,
+ struct perf_event_context *next)
+{
+ intel_pmu_lbr_swap_task_ctx(prev, next);
+}
+
static int intel_pmu_check_period(struct perf_event *event, u64 value)
{
return intel_pmu_has_bts_period(event, value) ? -EINVAL : 0;
@@ -3955,6 +3961,7 @@ static __initconst const struct x86_pmu intel_pmu = {
.guest_get_msrs = intel_guest_get_msrs,
.sched_task = intel_pmu_sched_task,
+ .swap_task_ctx = intel_pmu_swap_task_ctx,
.check_period = intel_pmu_check_period,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index f9a5d4356562..ed31aa849161 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3204,10 +3204,21 @@ static void perf_event_context_sched_out(struct
task_struct *task, int ctxn,
raw_spin_lock(&ctx->lock);
raw_spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING);
if (context_equiv(ctx, next_ctx)) {
+ struct pmu *pmu = ctx->pmu;
+
WRITE_ONCE(ctx->task, next);
WRITE_ONCE(next_ctx->task, task);
- swap(ctx->task_ctx_data, next_ctx->task_ctx_data);
+ /*
+ * PMU specific parts of task perf context can require
+ * additional synchronization. As an example of such
+ * synchronization see implementation details of Intel
+ * LBR call stack data profiling;
+ */
+ if (pmu->swap_task_ctx)
+ pmu->swap_task_ctx(ctx, next_ctx);
+ else
+ swap(ctx->task_ctx_data,
next_ctx->task_ctx_data);
/*
* RCU_INIT_POINTER here is safe because we've not
--
2.20.1
