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KVM: nVMX: Expose RDPMC-exiting only when guest supports PMU
Issue was discovered when running kvm-unit-tests on KVM running as L1 on top of Hyper-V. When vmx_instruction_intercept unit-test attempts to run RDPMC to test RDPMC-exiting, it is intercepted by L1 KVM which it's EXIT_REASON_RDPMC handler raise #GP because vCPU exposed by Hyper-V doesn't support PMU. Instead of unit-test expectation to be reflected with EXIT_REASON_RDPMC. The reason vmx_instruction_intercept unit-test attempts to run RDPMC even though Hyper-V doesn't support PMU is because L1 expose to L2 support for RDPMC-exiting. Which is reasonable to assume that is supported only in case CPU supports PMU to being with. Above issue can easily be simulated by modifying vmx_instruction_intercept config in x86/unittests.cfg to run QEMU with "-cpu host,+vmx,-pmu" and run unit-test. To handle issue, change KVM to expose RDPMC-exiting only when guest supports PMU. Reported-by: Saar Amar <saaramar@microsoft.com> Reviewed-by: Mihai Carabas <mihai.carabas@oracle.com> Reviewed-by: Jim Mattson <jmattson@google.com> Signed-off-by: Liran Alon <liran.alon@oracle.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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@ -6856,6 +6856,30 @@ static void nested_vmx_entry_exit_ctls_update(struct kvm_vcpu *vcpu)
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}
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}
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static bool guest_cpuid_has_pmu(struct kvm_vcpu *vcpu)
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{
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struct kvm_cpuid_entry2 *entry;
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union cpuid10_eax eax;
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entry = kvm_find_cpuid_entry(vcpu, 0xa, 0);
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if (!entry)
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return false;
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eax.full = entry->eax;
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return (eax.split.version_id > 0);
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}
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static void nested_vmx_procbased_ctls_update(struct kvm_vcpu *vcpu)
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{
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struct vcpu_vmx *vmx = to_vmx(vcpu);
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bool pmu_enabled = guest_cpuid_has_pmu(vcpu);
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if (pmu_enabled)
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vmx->nested.msrs.procbased_ctls_high |= CPU_BASED_RDPMC_EXITING;
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else
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vmx->nested.msrs.procbased_ctls_high &= ~CPU_BASED_RDPMC_EXITING;
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}
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static void update_intel_pt_cfg(struct kvm_vcpu *vcpu)
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{
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struct vcpu_vmx *vmx = to_vmx(vcpu);
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@ -6944,6 +6968,7 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
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if (nested_vmx_allowed(vcpu)) {
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nested_vmx_cr_fixed1_bits_update(vcpu);
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nested_vmx_entry_exit_ctls_update(vcpu);
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nested_vmx_procbased_ctls_update(vcpu);
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}
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if (boot_cpu_has(X86_FEATURE_INTEL_PT) &&
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