Re: [PATCH 2/2] powerpc/perf: Fix mmcra corruption by bhrb_filter

[Michael Ellerman]

On Sat, 2019-05-11 at 02:42:17 UTC, Ravi Bangoria wrote:
> Consider a scenario where user creates two events:
> 
>   1st event:
>     attr.sample_type |= PERF_SAMPLE_BRANCH_STACK;
>     attr.branch_sample_type = PERF_SAMPLE_BRANCH_ANY;
>     fd = perf_event_open(attr, 0, 1, -1, 0);
> 
>   This sets cpuhw->bhrb_filter to 0 and returns valid fd.
> 
>   2nd event:
>     attr.sample_type |= PERF_SAMPLE_BRANCH_STACK;
>     attr.branch_sample_type = PERF_SAMPLE_BRANCH_CALL;
>     fd = perf_event_open(attr, 0, 1, -1, 0);
> 
>   It overrides cpuhw->bhrb_filter to -1 and returns with error.
> 
> Now if power_pmu_enable() gets called by any path other than
> power_pmu_add(), ppmu->config_bhrb(-1) will set mmcra to -1.
> 
> Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx>
> Reviewed-by: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/3202e35ec1c8fc19cea24253ff83edf7

cheers