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| author |   Sean Christopherson <seanjc@google.com> | 2024-08-02 11:55:06 -0700 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2024-11-01 09:22:32 -0700 |
| commit | d75cac366f44174ab09b4d2ef16e70e6e30484e6 (patch) | |
| tree | 3a0332ffadde7fe66e8fc8547df99b66b341502c | |
| parent | KVM: x86: Quirk initialization of feature MSRs to KVM's max configuration (diff) | |
| download | wireguard-linux-d75cac366f44174ab09b4d2ef16e70e6e30484e6.tar.xz wireguard-linux-d75cac366f44174ab09b4d2ef16e70e6e30484e6.zip | |
KVM: x86: Reject userspace attempts to access PERF_CAPABILITIES w/o PDCM
Reject userspace accesses to PERF_CAPABILITIES if PDCM isn't set in guest
CPUID, i.e. if the vCPU doesn't actually have PERF_CAPABILITIES. But! Do
so via KVM_MSR_RET_UNSUPPORTED, so that reads get '0' and writes of '0'
are ignored if KVM advertised support PERF_CAPABILITIES.
KVM's ABI is that userspace must set guest CPUID prior to setting MSRs,
and that setting MSRs that aren't supposed exist is disallowed (modulo the
'0' exemption).
Link: https://lore.kernel.org/r/20240802185511.305849-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
| -rw-r--r-- | arch/x86/kvm/x86.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 34a7359d2bf3..c2802272871d 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3800,8 +3800,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) vcpu->arch.arch_capabilities = data; break; case MSR_IA32_PERF_CAPABILITIES: - if (!msr_info->host_initiated) - return 1; + if (!msr_info->host_initiated || + !guest_cpuid_has(vcpu, X86_FEATURE_PDCM)) + return KVM_MSR_RET_UNSUPPORTED; + if (data & ~kvm_caps.supported_perf_cap) return 1; @@ -4260,9 +4262,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) msr_info->data = vcpu->arch.arch_capabilities; break; case MSR_IA32_PERF_CAPABILITIES: - if (!msr_info->host_initiated && - !guest_cpuid_has(vcpu, X86_FEATURE_PDCM)) - return 1; + if (!guest_cpuid_has(vcpu, X86_FEATURE_PDCM)) + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.perf_capabilities; break; case MSR_IA32_POWER_CTL: |