On 10/13/2025 4:07 PM, Jani Nikula wrote:
On Mon, 13 Oct 2025, Chaitanya Kumar Borah <[email protected]>
wrote:
From: Dapeng Mi <[email protected]>
Explicitly zero kvm_host_pmu instead of attempting to get the perf PMU
capabilities when running on a hybrid CPU to avoid running afoul of perf's
sanity check.
------------[ cut here ]------------
WARNING: arch/x86/events/core.c:3089 at perf_get_x86_pmu_capability+0xd/0xc0,
Call Trace:
<TASK>
kvm_x86_vendor_init+0x1b0/0x1a40 [kvm]
vmx_init+0xdb/0x260 [kvm_intel]
vt_init+0x12/0x9d0 [kvm_intel]
do_one_initcall+0x60/0x3f0
do_init_module+0x97/0x2b0
load_module+0x2d08/0x2e30
init_module_from_file+0x96/0xe0
idempotent_init_module+0x117/0x330
__x64_sys_finit_module+0x73/0xe0
Always read the capabilities for non-hybrid CPUs, i.e. don't entirely
revert to reading capabilities if and only if KVM wants to use a PMU, as
it may be useful to have the host PMU capabilities available, e.g. if only
or debug.
Reported-by: Chaitanya Kumar Borah <[email protected]>
Closes:
https://lore.kernel.org/all/[email protected]/
Fixes: 51f34b1e650f ("KVM: x86/pmu: Snapshot host (i.e. perf's) reported PMU
capabilities")
Suggested-by: Sean Christopherson <[email protected]>
Signed-off-by: Dapeng Mi <[email protected]>
Link:
https://lore.kernel.org/r/[email protected]
[sean: rework changelog, call out hybrid CPUs in shortlog]
References: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15122
Signed-off-by: Sean Christopherson <[email protected]>
Chaitanya, please reply with your Signed-off-by, otherwise I can't merge
this. You *must* add your Signed-off-by even when sending someone else's
work unmodified.
Ack, please consider it
Signed-off-by: Chaitanya Kumar Borah <[email protected]>
Thank you for pointing it out.
BR,
Jani.
---
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) {
/*
