> On 1 Apr 2019, at 22:46, Jim Mattson <jmattson@xxxxxxxxxx> wrote: > > On Mon, Apr 1, 2019 at 7:51 AM Liran Alon <liran.alon@xxxxxxxxxx> wrote: >> >> Ping. >> >>> On 25 Mar 2019, at 21:09, Liran Alon <liran.alon@xxxxxxxxxx> wrote: >>> >>> 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@xxxxxxxxxxxxx> >>> Reviewed-by: Mihai Carabas <mihai.carabas@xxxxxxxxxx> >>> Signed-off-by: Liran Alon <liran.alon@xxxxxxxxxx> >>> --- >>> 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 f6915f10e584..2634ee8c9dc8 100644 >>> --- a/arch/x86/kvm/vmx/vmx.c >>> +++ b/arch/x86/kvm/vmx/vmx.c >>> @@ -6978,6 +6978,30 @@ 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; > > Doesn't this require that L0 supports RDPMC exiting, so that the bit > can be passed from vmcs12 to vmcs02? Looking at setup_vmcs_config(), CPU_BASED_RDPMC_EXITING is defined as part of minimum set of features that is required for KVM to run. So I can safely assume here that vmcs02 have RDPMC-exiting. Am I missing something? -Liran > >>> + 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); >>> @@ -7066,6 +7090,7 @@ 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 >>> >>