Re: [Patch v9 10/12] perf/x86/intel: Update dyn_constranit base on PEBS event precise level

[Peter Zijlstra]

On Fri, Nov 07, 2025 at 02:11:09PM +0800, Mi, Dapeng wrote:
> 
> On 11/6/2025 10:52 PM, Peter Zijlstra wrote:
> > On Wed, Oct 29, 2025 at 06:21:34PM +0800, Dapeng Mi wrote:
> >> arch-PEBS provides CPUIDs to enumerate which counters support PEBS
> >> sampling and precise distribution PEBS sampling. Thus PEBS constraints
> >> should be dynamically configured base on these counter and precise
> >> distribution bitmap instead of defining them statically.
> >>
> >> Update event dyn_constraint base on PEBS event precise level.
> > What happened to this:
> >
> >   https://lore.kernel.org/all/e0b25b3e-aec0-4c43-9ab2-907186b56c71@xxxxxxxxxxxxxxx/
> 
> About the issue, Kan ever posted a patch to mitigate the risk, but it seems
> the patch is not merged yet.
> 
> https://lore.kernel.org/all/20250512175542.2000708-1-kan.liang@xxxxxxxxxxxxxxx/

IIUC the below is what is required handle this new dynamic case, right?

--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -5423,6 +5423,8 @@ enum dyn_constr_type {
 	DYN_CONSTR_BR_CNTR,
 	DYN_CONSTR_ACR_CNTR,
 	DYN_CONSTR_ACR_CAUSE,
+	DYN_CONSTR_PEBS,
+	DYN_CONSTR_PDIST,
 
 	DYN_CONSTR_MAX,
 };
@@ -5432,6 +5434,8 @@ static const char * const dyn_constr_typ
 	[DYN_CONSTR_BR_CNTR] = "a branch counter logging event",
 	[DYN_CONSTR_ACR_CNTR] = "an auto-counter reload event",
 	[DYN_CONSTR_ACR_CAUSE] = "an auto-counter reload cause event",
+	[DYN_CONSTR_PEBS] = "a PEBS event",
+	[DYN_CONSTR_PDIST] = "a PEBS PDIST event",
 };
 
 static void __intel_pmu_check_dyn_constr(struct event_constraint *constr,
@@ -5536,6 +5540,14 @@ static void intel_pmu_check_dyn_constr(s
 				continue;
 			mask = hybrid(pmu, acr_cause_mask64) & GENMASK_ULL(INTEL_PMC_MAX_GENERIC - 1, 0);
 			break;
+		case DYN_CONSTR_PEBS:
+			if (x86_pmu.arch_pebs)
+				mask = hybrid(pmu, arch_pebs_cap).counters;
+			break;
+		case DYN_CONSTR_PDIST:
+			if (x86_pmu.arch_pebs)
+				mask = hybrid(pmu, arch_pebs_cap).pdists;
+			break;
 		default:
 			pr_warn("Unsupported dynamic constraint type %d\n", i);
 		}