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x86/perf: Fix CR4.PCE propagation to use active_mm instead of mm
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commit 5dc855d 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 <[email protected]>
Signed-off-by: Andy Lutomirski <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Fixes: 7911d3f ("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 <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
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@amluto @popcornmix
amluto authored and popcornmix committed Mar 23, 2017
1 parent 6c08057 commit 01303ee
Showing 1 changed file with 2 additions and 2 deletions.
4 changes: 2 additions & 2 deletions arch/x86/events/core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2096,8 +2096,8 @@ static int x86_pmu_event_init(struct perf_event *event)

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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