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 <[email protected]>
Reviewed-by: Kan Liang <[email protected]>
Reviewed-by: Andi Kleen <[email protected]>
---
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
