From: Liran Alon liran.alon@oracle.com
[ Upstream commit e51bfdb68725dc052d16241ace40ea3140f938aa ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- 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 34499081022c..0479aee38f4d 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6982,6 +6982,30 @@ 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); @@ -7070,6 +7094,7 @@ 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) &&