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Thu, 12 Feb 2026 06:43:54 -0800 (PST) X-Received: by 2002:a05:600c:350f:b0:483:4807:210c with SMTP id 5b1f17b1804b1-4836715a2bcmr39802065e9.24.1770907433753; Thu, 12 Feb 2026 06:43:53 -0800 (PST) From: Paolo Bonzini To: qemu-devel@nongnu.org Cc: Dongli Zhang , Xiaoyao Li , Zhao Liu , Dapeng Mi , Zide Chen Subject: [PULL 30/41] target/i386/kvm: set KVM_PMU_CAP_DISABLE if "-pmu" is configured Date: Thu, 12 Feb 2026 15:42:32 +0100 Message-ID: <20260212144244.22579-31-pbonzini@redhat.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260212144244.22579-1-pbonzini@redhat.com> References: <20260212144244.22579-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1770907462587158500 Content-Type: text/plain; charset="utf-8" From: Dongli Zhang 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 Reviewed-by: Zide Chen Link: https://lore.kernel.org/r/20260109075508.113097-2-dongli.zhang@oracle= .com Signed-off-by: Paolo Bonzini --- 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 0c940d4b640..69748420fd6 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 2.52.0