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charset="utf-8" Although AMD PERFCORE and PerfMonV2 are removed when "-pmu" is configured, there is no way to fully disable KVM AMD PMU virtualization. Neither "-cpu host,-pmu" nor "-cpu EPYC" achieves this. As a result, the following message still appears in the VM dmesg: [ 0.263615] Performance Events: AMD PMU driver. However, the expected output should be: [ 0.596381] Performance Events: PMU not available due to virtualization,= using software events only. [ 0.600972] NMI watchdog: Perf NMI watchdog permanently disabled This occurs because AMD does not use any CPUID bit to indicate PMU availability. To address this, KVM_CAP_PMU_CAPABILITY is used to set KVM_PMU_CAP_DISABLE when "-pmu" is configured. Signed-off-by: Dongli Zhang Reviewed-by: Xiaoyao Li Reviewed-by: Zhao Liu Reviewed-by: Dapeng Mi --- Changed since v1: - Switch back to the initial implementation with "-pmu". https://lore.kernel.org/all/20221119122901.2469-3-dongli.zhang@oracle.com - Mention that "KVM_PMU_CAP_DISABLE doesn't change the PMU behavior on Intel platform because current "pmu" property works as expected." Changed since v2: - Change has_pmu_cap to pmu_cap. - Use (pmu_cap & KVM_PMU_CAP_DISABLE) instead of only pmu_cap in if statement. - Add Reviewed-by from Xiaoyao and Zhao as the change is minor. Changed since v5: - Re-base on top of most recent mainline QEMU. - To resolve conflicts, move the PMU related code before the call site of is_tdx_vm(). Changed since v6: - Add Reviewed-by from Dapeng Mi. target/i386/kvm/kvm.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index 60c7981138..e5daa8c9fe 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -178,6 +178,8 @@ static int has_triple_fault_event; =20 static bool has_msr_mcg_ext_ctl; =20 +static int pmu_cap; + static struct kvm_cpuid2 *cpuid_cache; static struct kvm_cpuid2 *hv_cpuid_cache; static struct kvm_msr_list *kvm_feature_msrs; @@ -2079,6 +2081,33 @@ full: =20 int kvm_arch_pre_create_vcpu(CPUState *cpu, Error **errp) { + static bool first =3D true; + int ret; + + if (first) { + first =3D false; + + /* + * Since Linux v5.18, KVM provides a VM-level capability to easily + * disable PMUs; however, QEMU has been providing PMU property per + * CPU since v1.6. In order to accommodate both, have to configure + * the VM-level capability here. + * + * KVM_PMU_CAP_DISABLE doesn't change the PMU + * behavior on Intel platform because current "pmu" property works + * as expected. + */ + if ((pmu_cap & KVM_PMU_CAP_DISABLE) && !X86_CPU(cpu)->enable_pmu) { + ret =3D kvm_vm_enable_cap(kvm_state, KVM_CAP_PMU_CAPABILITY, 0, + KVM_PMU_CAP_DISABLE); + if (ret < 0) { + error_setg_errno(errp, -ret, + "Failed to set KVM_PMU_CAP_DISABLE"); + return ret; + } + } + } + if (is_tdx_vm()) { return tdx_pre_create_vcpu(cpu, errp); } @@ -3390,6 +3419,8 @@ int kvm_arch_init(MachineState *ms, KVMState *s) } } =20 + pmu_cap =3D kvm_check_extension(s, KVM_CAP_PMU_CAPABILITY); + return 0; } =20 --=20 2.39.3