When load KVM module in Intel hybrid platforms, the warning below is
observed.

<4>[   10.973827] ------------[ cut here ]------------
<4>[   10.973841] WARNING: arch/x86/events/core.c:3089 at
perf_get_x86_pmu_capability+0xd/0xc0, CPU#15: (udev-worker)/386
...
<4>[   10.974028] Call Trace:
<4>[   10.974030]  <TASK>
<4>[   10.974033]  ? kvm_init_pmu_capability+0x2b/0x190 [kvm]
<4>[   10.974154]  kvm_x86_vendor_init+0x1b0/0x1a40 [kvm]
<4>[   10.974248]  vmx_init+0xdb/0x260 [kvm_intel]
<4>[   10.974278]  ? __pfx_vt_init+0x10/0x10 [kvm_intel]
<4>[   10.974296]  vt_init+0x12/0x9d0 [kvm_intel]
<4>[   10.974309]  ? __pfx_vt_init+0x10/0x10 [kvm_intel]
<4>[   10.974322]  do_one_initcall+0x60/0x3f0
<4>[   10.974335]  do_init_module+0x97/0x2b0
<4>[   10.974345]  load_module+0x2d08/0x2e30
<4>[   10.974349]  ? __kernel_read+0x158/0x2f0
<4>[   10.974370]  ? kernel_read_file+0x2b1/0x320
<4>[   10.974381]  init_module_from_file+0x96/0xe0
<4>[   10.974384]  ? init_module_from_file+0x96/0xe0
<4>[   10.974399]  idempotent_init_module+0x117/0x330
<4>[   10.974415]  __x64_sys_finit_module+0x73/0xe0

The root cause is the helper perf_get_x86_pmu_capability() is called
unconditionally but it's supposed to be called only on non-hybrid
platforms.

This patch fixes this warning by only calling
perf_get_x86_pmu_capability() on non-hybrid platforms.

Reported-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Closes: https://lore.kernel.org/all/70b64347-2aca-4511-af78-a767d5fa8226@intel.com/
Fixes: 51f34b1e650f ("KVM: x86/pmu: Snapshot host (i.e. perf's) reported PMU capabilities")
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---
 arch/x86/kvm/pmu.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 40ac4cb44ed2..487ad19a236e 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -108,16 +108,18 @@ void kvm_init_pmu_capability(const struct kvm_pmu_ops *pmu_ops)
 	bool is_intel = boot_cpu_data.x86_vendor == X86_VENDOR_INTEL;
 	int min_nr_gp_ctrs = pmu_ops->MIN_NR_GP_COUNTERS;
 
-	perf_get_x86_pmu_capability(&kvm_host_pmu);
-
 	/*
 	 * Hybrid PMUs don't play nice with virtualization without careful
 	 * configuration by userspace, and KVM's APIs for reporting supported
 	 * vPMU features do not account for hybrid PMUs.  Disable vPMU support
 	 * for hybrid PMUs until KVM gains a way to let userspace opt-in.
 	 */
-	if (cpu_feature_enabled(X86_FEATURE_HYBRID_CPU))
+	if (cpu_feature_enabled(X86_FEATURE_HYBRID_CPU)) {
 		enable_pmu = false;
+		memset(&kvm_host_pmu, 0, sizeof(kvm_host_pmu));
+	} else {
+		perf_get_x86_pmu_capability(&kvm_host_pmu);
+	}
 
 	if (enable_pmu) {
 		/*
-- 
2.34.1

On Fri, 10 Oct 2025 08:52:39 +0800, Dapeng Mi wrote:
> When load KVM module in Intel hybrid platforms, the warning below is
> observed.
>
> [...]

Applied to kvm-x86 fixes, with a different shortlog and changelog.  I wanted to
call out that the fix is for hybrid CPUs, and that snapshotting PMU capabilities
for non-hybrid CPUs even if enable_pmu=false is intentional.

Thanks much!

[1/1] KVM: x86/pmu: Don't try to get perf capabilities for hybrid CPUs
      https://github.com/kvm-x86/linux/commit/034417c1439a

--
https://github.com/kvm-x86/linux/tree/next