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@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Kan Liang <kan.liang@linux.intel.com>
Link: https://lkml.kernel.org/r/YMsy7BuGT8nBTspT@hirez.programming.kicks-ass.net

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6c964de..0e125ae 100644 (file)
--- 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);