From e51bfdb68725dc052d16241ace40ea3140f938aa Mon Sep 17 00:00:00 2001 From: Liran Alon Date: Mon, 25 Mar 2019 21:09:17 +0200 Subject: [PATCH] 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 Reviewed-by: Mihai Carabas Reviewed-by: Jim Mattson Signed-off-by: Liran Alon Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/vmx.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 88060a621db2..5866e9e9f1e0 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6856,6 +6856,30 @@ static void nested_vmx_entry_exit_ctls_update(struct kvm_vcpu *vcpu) } } +static bool guest_cpuid_has_pmu(struct kvm_vcpu *vcpu) +{ + struct kvm_cpuid_entry2 *entry; + union cpuid10_eax eax; + + entry = kvm_find_cpuid_entry(vcpu, 0xa, 0); + if (!entry) + return false; + + eax.full = entry->eax; + return (eax.split.version_id > 0); +} + +static void nested_vmx_procbased_ctls_update(struct kvm_vcpu *vcpu) +{ + struct vcpu_vmx *vmx = to_vmx(vcpu); + bool pmu_enabled = guest_cpuid_has_pmu(vcpu); + + if (pmu_enabled) + vmx->nested.msrs.procbased_ctls_high |= CPU_BASED_RDPMC_EXITING; + else + vmx->nested.msrs.procbased_ctls_high &= ~CPU_BASED_RDPMC_EXITING; +} + static void update_intel_pt_cfg(struct kvm_vcpu *vcpu) { struct vcpu_vmx *vmx = to_vmx(vcpu); @@ -6944,6 +6968,7 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu) if (nested_vmx_allowed(vcpu)) { nested_vmx_cr_fixed1_bits_update(vcpu); nested_vmx_entry_exit_ctls_update(vcpu); + nested_vmx_procbased_ctls_update(vcpu); } if (boot_cpu_has(X86_FEATURE_INTEL_PT) && -- 2.20.1