[tip: perf/core] perf: Fix task context PMU for Hetero

From: tip-bot2 for Peter Zijlstra
Date: Thu Jun 24 2021 - 03:09:52 EST

The following commit has been merged into the perf/core branch of tip:

Commit-ID: 012669c740e6e2afa8bdb95394d06676f933dd2d
Gitweb: https://git.kernel.org/tip/012669c740e6e2afa8bdb95394d06676f933dd2d
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Tue, 22 Jun 2021 16:21:01 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 23 Jun 2021 18:30:56 +02:00

perf: Fix task context PMU for Hetero

On HETEROGENEOUS hardware (ARM big.Little, Intel Alderlake etc.) each
CPU might have a different hardware PMU. Since each such PMU is
represented by a different struct pmu, but we only have a single HW
task context.

That means that the task context needs to switch PMU type when it
switches CPUs.

Not doing this means that ctx->pmu calls (pmu_{dis,en}able(),
{start,commit,cancel}_txn() etc.) are called against the wrong PMU and
things will go wobbly.

Fixes: f83d2f91d259 ("perf/x86/intel: Add Alder Lake Hybrid support")
Reported-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/YMsy7BuGT8nBTspT@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
kernel/events/core.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6c964de..0e125ae 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3822,9 +3822,16 @@ static void perf_event_context_sched_in(struct perf_event_context *ctx,
struct task_struct *task)
struct perf_cpu_context *cpuctx;
- struct pmu *pmu = ctx->pmu;
+ struct pmu *pmu;

cpuctx = __get_cpu_context(ctx);
+ /*
+ * HACK: for HETEROGENEOUS the task context might have switched to a
+ * different PMU, force (re)set the context,
+ */
+ pmu = ctx->pmu = cpuctx->ctx.pmu;
if (cpuctx->task_ctx == ctx) {
if (cpuctx->sched_cb_usage)
__perf_pmu_sched_task(cpuctx, true);