On 1/17/2026 9:10 AM, Zide Chen wrote:
> Guest PMU support requires KVM. Clear cpu->enable_pmu when KVM is not
> enabled, so PMU-related code can rely solely on cpu->enable_pmu.
>
> This reduces duplication and avoids bugs where one of the checks is
> missed. For example, cpu_x86_cpuid() enables CPUID.0AH when
> cpu->enable_pmu is set but does not check kvm_enabled(). This is
> implicitly fixed by this patch:
>
> if (cpu->enable_pmu) {
> x86_cpu_get_supported_cpuid(0xA, count, eax, ebx, ecx, edx);
> }
>
> Also fix two places that check kvm_enabled() but not cpu->enable_pmu.
>
> Signed-off-by: Zide Chen <[email protected]>
> ---
> target/i386/cpu.c | 9 ++++++---
> target/i386/kvm/kvm.c | 4 ++--
> 2 files changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 37803cd72490..f1ac98970d3e 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -8671,7 +8671,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
> uint32_t count,
> *ecx = 0;
> *edx = 0;
> if (!(env->features[FEAT_7_0_EBX] & CPUID_7_0_EBX_INTEL_PT) ||
> - !kvm_enabled()) {
> + !cpu->enable_pmu) {
> break;
> }
>
> @@ -9018,7 +9018,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
> uint32_t count,
> case 0x80000022:
> *eax = *ebx = *ecx = *edx = 0;
> /* AMD Extended Performance Monitoring and Debug */
> - if (kvm_enabled() && cpu->enable_pmu &&
> + if (cpu->enable_pmu &&
> (env->features[FEAT_8000_0022_EAX] &
> CPUID_8000_0022_EAX_PERFMON_V2)) {
> *eax |= CPUID_8000_0022_EAX_PERFMON_V2;
> *ebx |= kvm_arch_get_supported_cpuid(cs->kvm_state, index, count,
> @@ -9642,7 +9642,7 @@ static bool x86_cpu_filter_features(X86CPU *cpu, bool
> verbose)
> * are advertised by cpu_x86_cpuid(). Keep these two in sync.
> */
> if ((env->features[FEAT_7_0_EBX] & CPUID_7_0_EBX_INTEL_PT) &&
> - kvm_enabled()) {
> + cpu->enable_pmu) {
> x86_cpu_get_supported_cpuid(0x14, 0,
> &eax_0, &ebx_0, &ecx_0, &edx_0);
> x86_cpu_get_supported_cpuid(0x14, 1,
> @@ -9790,6 +9790,9 @@ static void x86_cpu_realizefn(DeviceState *dev, Error
> **errp)
> Error *local_err = NULL;
> unsigned requested_lbr_fmt;
>
> + if (!kvm_enabled())
> + cpu->enable_pmu = false;
> +
> #if defined(CONFIG_TCG) && !defined(CONFIG_USER_ONLY)
> /* Use pc-relative instructions in system-mode */
> tcg_cflags_set(cs, CF_PCREL);
> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> index cffbc90d1c50..e81fa46ed66c 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -4222,7 +4222,7 @@ static int kvm_put_msrs(X86CPU *cpu, KvmPutState level)
> env->msr_xfd_err);
> }
>
> - if (kvm_enabled() && cpu->enable_pmu &&
> + if (cpu->enable_pmu &&
> (env->features[FEAT_7_0_EDX] & CPUID_7_0_EDX_ARCH_LBR)) {
> uint64_t depth;
> int ret;
> @@ -4698,7 +4698,7 @@ static int kvm_get_msrs(X86CPU *cpu)
> kvm_msr_entry_add(cpu, MSR_IA32_XFD_ERR, 0);
> }
>
> - if (kvm_enabled() && cpu->enable_pmu &&
> + if (cpu->enable_pmu &&
> (env->features[FEAT_7_0_EDX] & CPUID_7_0_EDX_ARCH_LBR)) {
> uint64_t depth;
>
LGTM.
Reviewed-by: Dapeng Mi <[email protected]>
