lkml.org 
[lkml]   [2021]   [Mar]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v4 RESEND 2/5] perf/x86/lbr: Simplify the exposure check for the LBR_INFO registers
From
Date
On 2021/3/24 5:38, Peter Zijlstra wrote:
> On Mon, Mar 22, 2021 at 02:06:32PM +0800, 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
>
> You mean: intel_pmu_lbr_*init*(). '?' is a single character glob and
> you've got too many '_'s.
>
>> in the x86_perf_get_lbr() directly, instead of relying on lbr_format check.
>
> But, afaict, not every model calls one of those. CORE_YONAH for example
> doesn't.
>
>> 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.
>
> Relevance?
>
> Wouldn't it be much simpler to simple say something like:
>
> "x86_pmu.lbr_info is 0 unless explicitly initialized, so there's no
> point checking lbr_fmt"

Yes, it is simpler and I will apply it in the next version.

>
>> Signed-off-by: Like Xu <like.xu@linux.intel.com>
>> Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
>> Reviewed-by: Andi Kleen <ak@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
>>

\
 
 \ /
  Last update: 2021-03-24 03:03    [W:0.100 / U:0.528 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site