On 23/12/2022 1:41 am, Sean Christopherson wrote:
On Thu, Dec 22, 2022, Like Xu wrote:
Hi Peter, would you help apply this one in your tip/perf tree,
as it doesn't seem to be closely tied to the KVM changes. Thanks.
On 25/11/2022 12:05 pm, Yang Weijiang wrote:
From: Like Xu <like.xu@xxxxxxxxxxxxxxx>
The x86_pmu.lbr_info is 0 unless explicitly initialized, so there's
no point checking x86_pmu.intel_cap.lbr_format.
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Reviewed-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
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 4dbde69c423b..e7caabfa1377 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -1606,12 +1606,10 @@ void __init intel_pmu_arch_lbr_init(void)
*/
void 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;
This stable-worthy a bug fix, no? E.g. won't the existing code misreport lbr->info
if the format is LBR_FORMAT_INFO2?
Sure, we need "Cc: stable@xxxxxxxxxxxxxxx" in order not to lose misprediction
and cycles
information on the LBR_FORMAT_INFO2 platforms like Goldmont plus.
}
EXPORT_SYMBOL_GPL(x86_perf_get_lbr);
