Re: [PATCH V4 1/2] perf ignore LBR and extra_regs.

[Peter Zijlstra]

On Tue, Jul 08, 2014 at 09:49:40AM -0700, kan.li...@intel.com wrote:
> diff --git a/arch/x86/kernel/cpu/perf_event.c 
> b/arch/x86/kernel/cpu/perf_event.c
> index 2bdfbff..f0e8022 100644
> --- a/arch/x86/kernel/cpu/perf_event.c
> +++ b/arch/x86/kernel/cpu/perf_event.c
> @@ -118,6 +118,9 @@ static int x86_pmu_extra_regs(u64 config, struct 
> perf_event *event)
>                       continue;
>               if (event->attr.config1 & ~er->valid_mask)
>                       return -EINVAL;
> +             /* Check if the extra msrs can be safely accessed*/
> +             if (!x86_pmu.extra_msr_access[er->idx])
> +                     continue;
>  
>               reg->idx = er->idx;
>               reg->config = event->attr.config1;

You should return an error here; doing continue will eventually make
it return 0, which is no-error and things will happily create the event
and malfunction.

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