[PATCH] perf/x86/lbr: Simplify the exposure check for the LBR_INFO registers

[PATCH] perf/x86/lbr: Simplify the exposure check for the LBR_INFO registers

[Like Xu]

If the platform supports LBR_INFO register, the x86_pmu.lbr_info will
be assigned in intel_pmu_?_lbr_init_?() and it's safe to expose LBR_INFO
in the x86_perf_get_lbr() directly, instead of relying on lbr_format check.

Also Architectural LBR has IA32_LBR_x_INFO instead of LBR_FORMAT_INFO_x
to hold metadata for the operation, including mispredict, TSX, and
elapsed cycle time information.

Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Like Xu <like.xu@linux.intel.com>
---
 arch/x86/events/intel/lbr.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index 21890dacfcfe..355ea70f1879 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -1832,12 +1832,10 @@ void __init intel_pmu_arch_lbr_init(void)
  */
 int x86_perf_get_lbr(struct x86_pmu_lbr *lbr)
 {
-	int lbr_fmt = x86_pmu.intel_cap.lbr_format;
-
 	lbr->nr = x86_pmu.lbr_nr;
 	lbr->from = x86_pmu.lbr_from;
 	lbr->to = x86_pmu.lbr_to;
-	lbr->info = (lbr_fmt == LBR_FORMAT_INFO) ? x86_pmu.lbr_info : 0;
+	lbr->info = x86_pmu.lbr_info;
 
 	return 0;
 }
-- 
2.29.2

Re: [PATCH] perf/x86/lbr: Simplify the exposure check for the LBR_INFO registers

[Like Xu]

Hi Peter,

Would you help pick up this patch so that we can enable guest Arch LBR?

---
thx,likexu

On 2021/2/3 15:03, Like Xu wrote:
> If the platform supports LBR_INFO register, the x86_pmu.lbr_info will
> be assigned in intel_pmu_?_lbr_init_?() and it's safe to expose LBR_INFO
> in the x86_perf_get_lbr() directly, instead of relying on lbr_format check.
> 
> Also Architectural LBR has IA32_LBR_x_INFO instead of LBR_FORMAT_INFO_x
> to hold metadata for the operation, including mispredict, TSX, and
> elapsed cycle time information.
> 
> Cc: Kan Liang <kan.liang@linux.intel.com>
> Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
> Signed-off-by: Like Xu <like.xu@linux.intel.com>
> ---
>   arch/x86/events/intel/lbr.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
> index 21890dacfcfe..355ea70f1879 100644
> --- a/arch/x86/events/intel/lbr.c
> +++ b/arch/x86/events/intel/lbr.c
> @@ -1832,12 +1832,10 @@ void __init intel_pmu_arch_lbr_init(void)
>    */
>   int x86_perf_get_lbr(struct x86_pmu_lbr *lbr)
>   {
> -	int lbr_fmt = x86_pmu.intel_cap.lbr_format;
> -
>   	lbr->nr = x86_pmu.lbr_nr;
>   	lbr->from = x86_pmu.lbr_from;
>   	lbr->to = x86_pmu.lbr_to;
> -	lbr->info = (lbr_fmt == LBR_FORMAT_INFO) ? x86_pmu.lbr_info : 0;
> +	lbr->info = x86_pmu.lbr_info;
>   
>   	return 0;
>   }
>