This is a note to let you know that I've just added the patch titled
perf/x86: Refuse to export capabilities for hybrid PMUs
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
perf-x86-refuse-to-export-capabilities-for-hybrid-pmus.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4b4191b8ae1278bde3642acaaef8f92810ed111a Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@xxxxxxxxxx>
Date: Wed, 8 Feb 2023 20:42:30 +0000
Subject: perf/x86: Refuse to export capabilities for hybrid PMUs
From: Sean Christopherson <seanjc@xxxxxxxxxx>
commit 4b4191b8ae1278bde3642acaaef8f92810ed111a upstream.
Now that KVM disables vPMU support on hybrid CPUs, WARN and return zeros
if perf_get_x86_pmu_capability() is invoked on a hybrid CPU. The helper
doesn't provide an accurate accounting of the PMU capabilities for hybrid
CPUs and needs to be enhanced if KVM, or anything else outside of perf,
wants to act on the PMU capabilities.
Cc: stable@xxxxxxxxxxxxxxx
Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/all/20220818181530.2355034-1-kan.liang@xxxxxxxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Message-Id: <20230208204230.1360502-3-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/events/core.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2994,17 +2994,19 @@ unsigned long perf_misc_flags(struct pt_
void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap)
{
- if (!x86_pmu_initialized()) {
+ /* This API doesn't currently support enumerating hybrid PMUs. */
+ if (WARN_ON_ONCE(cpu_feature_enabled(X86_FEATURE_HYBRID_CPU)) ||
+ !x86_pmu_initialized()) {
memset(cap, 0, sizeof(*cap));
return;
}
- cap->version = x86_pmu.version;
/*
- * KVM doesn't support the hybrid PMU yet.
- * Return the common value in global x86_pmu,
- * which available for all cores.
+ * Note, hybrid CPU models get tracked as having hybrid PMUs even when
+ * all E-cores are disabled via BIOS. When E-cores are disabled, the
+ * base PMU holds the correct number of counters for P-cores.
*/
+ cap->version = x86_pmu.version;
cap->num_counters_gp = x86_pmu.num_counters;
cap->num_counters_fixed = x86_pmu.num_counters_fixed;
cap->bit_width_gp = x86_pmu.cntval_bits;
Patches currently in stable-queue which might be from seanjc@xxxxxxxxxx are
queue-6.1/perf-x86-refuse-to-export-capabilities-for-hybrid-pmus.patch
queue-6.1/kvm-x86-pmu-disable-vpmu-support-on-hybrid-cpus-host-pmus.patch
queue-6.1/kvm-initialize-all-of-the-kvm_debugregs-structure-before-sending-it-to-userspace.patch
