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| author | Sean Christopherson <seanjc@google.com> | 2022-06-08 01:23:51 +0200 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2022-12-01 01:29:53 +0100 |
| commit | d2a00af2061db863890e32a4a99a6f82c330df1f (patch) | |
| tree | 73658f1e257ff94d7cf1dd2157090426601e956e /arch/x86/kvm | |
| parent | KVM: VMX: Make vmread_error_trampoline() uncallable from C code (diff) | |
| download | linux-d2a00af2061db863890e32a4a99a6f82c330df1f.tar.xz linux-d2a00af2061db863890e32a4a99a6f82c330df1f.zip | |
KVM: VMX: Allow userspace to set all supported FEATURE_CONTROL bits
Allow userspace to set all supported bits in MSR IA32_FEATURE_CONTROL
irrespective of the guest CPUID model, e.g. via KVM_SET_MSRS. KVM's ABI
is that userspace is allowed to set MSRs before CPUID, i.e. can set MSRs
to values that would fault according to the guest CPUID model.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220607232353.3375324-2-seanjc@google.com
Diffstat (limited to 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 36 |
1 files changed, 31 insertions, 5 deletions
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 3f31c46c306e..7be1fb50a753 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1836,12 +1836,38 @@ bool nested_vmx_allowed(struct kvm_vcpu *vcpu) return nested && guest_cpuid_has(vcpu, X86_FEATURE_VMX); } -static inline bool vmx_feature_control_msr_valid(struct kvm_vcpu *vcpu, - uint64_t val) +/* + * Userspace is allowed to set any supported IA32_FEATURE_CONTROL regardless of + * guest CPUID. Note, KVM allows userspace to set "VMX in SMX" to maintain + * backwards compatibility even though KVM doesn't support emulating SMX. And + * because userspace set "VMX in SMX", the guest must also be allowed to set it, + * e.g. if the MSR is left unlocked and the guest does a RMW operation. + */ +#define KVM_SUPPORTED_FEATURE_CONTROL (FEAT_CTL_LOCKED | \ + FEAT_CTL_VMX_ENABLED_INSIDE_SMX | \ + FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX | \ + FEAT_CTL_SGX_LC_ENABLED | \ + FEAT_CTL_SGX_ENABLED | \ + FEAT_CTL_LMCE_ENABLED) + +static inline bool vmx_feature_control_msr_valid(struct vcpu_vmx *vmx, + struct msr_data *msr) { - uint64_t valid_bits = to_vmx(vcpu)->msr_ia32_feature_control_valid_bits; + uint64_t valid_bits; + + /* + * Ensure KVM_SUPPORTED_FEATURE_CONTROL is updated when new bits are + * exposed to the guest. + */ + WARN_ON_ONCE(vmx->msr_ia32_feature_control_valid_bits & + ~KVM_SUPPORTED_FEATURE_CONTROL); + + if (msr->host_initiated) + valid_bits = KVM_SUPPORTED_FEATURE_CONTROL; + else + valid_bits = vmx->msr_ia32_feature_control_valid_bits; - return !(val & ~valid_bits); + return !(msr->data & ~valid_bits); } static int vmx_get_msr_feature(struct kvm_msr_entry *msr) @@ -2240,7 +2266,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) vcpu->arch.mcg_ext_ctl = data; break; case MSR_IA32_FEAT_CTL: - if (!vmx_feature_control_msr_valid(vcpu, data) || + if (!vmx_feature_control_msr_valid(vmx, msr_info) || (to_vmx(vcpu)->msr_ia32_feature_control & FEAT_CTL_LOCKED && !msr_info->host_initiated)) return 1; |