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    Subject[PATCH 4.10 58/63] x86/perf: Fix CR4.PCE propagation to use active_mm instead of mm
    Date
    4.10-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Andy Lutomirski <luto@kernel.org>

    commit 5dc855d44c2ad960a86f593c60461f1ae1566b6d upstream.

    If one thread mmaps a perf event while another thread in the same mm
    is in some context where active_mm != mm (which can happen in the
    scheduler, for example), refresh_pce() would write the wrong value
    to CR4.PCE. This broke some PAPI tests.

    Reported-and-tested-by: Vince Weaver <vincent.weaver@maine.edu>
    Signed-off-by: Andy Lutomirski <luto@kernel.org>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Borislav Petkov <bpetkov@suse.de>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephane Eranian <eranian@google.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Fixes: 7911d3f7af14 ("perf/x86: Only allow rdpmc if a perf_event is mapped")
    Link: http://lkml.kernel.org/r/0c5b38a76ea50e405f9abe07a13dfaef87c173a1.1489694270.git.luto@kernel.org
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/events/core.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/arch/x86/events/core.c
    +++ b/arch/x86/events/core.c
    @@ -2100,8 +2100,8 @@ static int x86_pmu_event_init(struct per

    static void refresh_pce(void *ignored)
    {
    - if (current->mm)
    - load_mm_cr4(current->mm);
    + if (current->active_mm)
    + load_mm_cr4(current->active_mm);
    }

    static void x86_pmu_event_mapped(struct perf_event *event)

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