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| author | Liran Alon <liran.alon@oracle.com> | 2019-03-25 21:09:17 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2019-04-16 15:37:34 +0200 |
| commit | e51bfdb68725dc052d16241ace40ea3140f938aa (patch) | |
| tree | 3413e07454f91e271d62cc6a71af4fe9ffc6f577 /arch | |
| parent | 672ff6cff80ca43bf3258410d2b887036969df5f (diff) | |
| download | lwn-e51bfdb68725dc052d16241ace40ea3140f938aa.tar.gz lwn-e51bfdb68725dc052d16241ace40ea3140f938aa.zip | |
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>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 25 |
1 files changed, 25 insertions, 0 deletions
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) && |