Re: [PATCH v3 3/3] x86: Check platform vPMU capabilities before run lbr tests

[Sean Christopherson <seanjc@google.com>]

On Fri, Jun 24, 2022, Yang Weijiang wrote:
> Use new helper to check whether pmu is available and Perfmon/Debug
> capbilities are supported before read MSR_IA32_PERF_CAPABILITIES to
> avoid test failure. The issue can be captured when enable_pmu=0.
> 
> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> ---
>  lib/x86/processor.h |  2 +-
>  x86/pmu_lbr.c       | 32 +++++++++++++-------------------
>  2 files changed, 14 insertions(+), 20 deletions(-)
> 
> diff --git a/lib/x86/processor.h b/lib/x86/processor.h
> index 70b9193..bb917b0 100644
> --- a/lib/x86/processor.h
> +++ b/lib/x86/processor.h
> @@ -193,7 +193,7 @@ static inline bool is_intel(void)
>  #define X86_FEATURE_PAUSEFILTER     (CPUID(0x8000000A, 0, EDX, 10))
>  #define X86_FEATURE_PFTHRESHOLD     (CPUID(0x8000000A, 0, EDX, 12))
>  #define	X86_FEATURE_VGIF		(CPUID(0x8000000A, 0, EDX, 16))
> -
> +#define	X86_FEATURE_PDCM		(CPUID(0x1, 0, ECX, 15))

Please try to think critically about the code you're writing.  All of the existing
X86_FEATURE_* definitions are organized by leaf, sub-leaf, register _and_ bit
position.  And now there's X86_FEATURE_PDCM...