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    Subject[PATCH 5.13 346/800] perf: Fix task context PMU for Hetero
    Date
    From: Peter Zijlstra <peterz@infradead.org>

    [ Upstream commit 012669c740e6e2afa8bdb95394d06676f933dd2d ]

    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
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 fe88d6eea3c2..9ebac2a79467 100644
    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -3821,9 +3821,16 @@ 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);
    --
    2.30.2


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