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;

If you fail here;

>               reg->idx = er->idx;
>               reg->config = event->attr.config1;

> diff --git a/arch/x86/kernel/cpu/perf_event_intel.c 
> b/arch/x86/kernel/cpu/perf_event_intel.c
> index adb02aa..2be44be 100644
> --- a/arch/x86/kernel/cpu/perf_event_intel.c
> +++ b/arch/x86/kernel/cpu/perf_event_intel.c
> @@ -1471,11 +1471,14 @@ static void intel_fixup_er(struct perf_event *event, 
> int idx)
>  {
>       event->hw.extra_reg.idx = idx;
>  
> -     if (idx == EXTRA_REG_RSP_0) {
> +     /* The extra_reg doesn't update if msrs cannot be accessed safely */
> +     if ((idx == EXTRA_REG_RSP_0) &&
> +                     x86_pmu.extra_msr_access[EXTRA_REG_RSP_0]) {
>               event->hw.config &= ~INTEL_ARCH_EVENT_MASK;
>               event->hw.config |= x86_pmu.extra_regs[EXTRA_REG_RSP_0].event;
>               event->hw.extra_reg.reg = MSR_OFFCORE_RSP_0;
> -     } else if (idx == EXTRA_REG_RSP_1) {
> +     } else if ((idx == EXTRA_REG_RSP_1) &&
> +                     x86_pmu.extra_msr_access[EXTRA_REG_RSP_1]) {
>               event->hw.config &= ~INTEL_ARCH_EVENT_MASK;
>               event->hw.config |= x86_pmu.extra_regs[EXTRA_REG_RSP_1].event;
>               event->hw.extra_reg.reg = MSR_OFFCORE_RSP_1;

You should never get here..

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