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: f83d2f9 ("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

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);