github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-28 17:13:52 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

KVM: x86: Reject userspace attempts to access PERF_CAPABILITIES w/o PDCM

Browse Source 
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>
This commit is contained in:
Sean Christopherson 2024-08-02 11:55:06 -07:00
parent dcb988cdac
commit d75cac366f
1 changed files with 6 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
arch/x86/kvm/x86.c
View File

@ -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: