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.
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) {
> /*
--
Jani Nikula, Intel
