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authorSean Christopherson <sean.j.christopherson@intel.com>2019-04-02 08:19:15 -0700
committerPaolo Bonzini <pbonzini@redhat.com>2019-04-16 15:39:07 +0200
commit11988499e62b310f3bf6f6d0a807a06d3f9ccc96 (patch)
tree15b10aaa497dd7e4308278168361612b1baec035
parentc80add0f487e28c48e855245189dc28bd3d5c250 (diff)
KVM: x86: Skip EFER vs. guest CPUID checks for host-initiated writes
KVM allows userspace to violate consistency checks related to the guest's CPUID model to some degree. Generally speaking, userspace has carte blanche when it comes to guest state so long as jamming invalid state won't negatively affect the host. Currently this is seems to be a non-issue as most of the interesting EFER checks are missing, e.g. NX and LME, but those will be added shortly. Proactively exempt userspace from the CPUID checks so as not to break userspace. Note, the efer_reserved_bits check still applies to userspace writes as that mask reflects the host's capabilities, e.g. KVM shouldn't allow a guest to run with NX=1 if it has been disabled in the host. Fixes: d80174745ba39 ("KVM: SVM: Only allow setting of EFER_SVME when CPUID SVM is set") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/kvm/x86.c37
1 files changed, 24 insertions, 13 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a0d1fc80ac5a..5d7dcd06d08a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1258,31 +1258,42 @@ static int do_get_msr_feature(struct kvm_vcpu *vcpu, unsigned index, u64 *data)
return 0;
}
-bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer)
+static bool __kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer)
{
- if (efer & efer_reserved_bits)
- return false;
-
if (efer & EFER_FFXSR && !guest_cpuid_has(vcpu, X86_FEATURE_FXSR_OPT))
- return false;
+ return false;
if (efer & EFER_SVME && !guest_cpuid_has(vcpu, X86_FEATURE_SVM))
- return false;
+ return false;
return true;
+
+}
+bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer)
+{
+ if (efer & efer_reserved_bits)
+ return false;
+
+ return __kvm_valid_efer(vcpu, efer);
}
EXPORT_SYMBOL_GPL(kvm_valid_efer);
-static int set_efer(struct kvm_vcpu *vcpu, u64 efer)
+static int set_efer(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
{
u64 old_efer = vcpu->arch.efer;
+ u64 efer = msr_info->data;
- if (!kvm_valid_efer(vcpu, efer))
- return 1;
+ if (efer & efer_reserved_bits)
+ return false;
- if (is_paging(vcpu)
- && (vcpu->arch.efer & EFER_LME) != (efer & EFER_LME))
- return 1;
+ if (!msr_info->host_initiated) {
+ if (!__kvm_valid_efer(vcpu, efer))
+ return 1;
+
+ if (is_paging(vcpu) &&
+ (vcpu->arch.efer & EFER_LME) != (efer & EFER_LME))
+ return 1;
+ }
efer &= ~EFER_LMA;
efer |= vcpu->arch.efer & EFER_LMA;
@@ -2452,7 +2463,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
vcpu->arch.arch_capabilities = data;
break;
case MSR_EFER:
- return set_efer(vcpu, data);
+ return set_efer(vcpu, msr_info);
case MSR_K7_HWCR:
data &= ~(u64)0x40; /* ignore flush filter disable */
data &= ~(u64)0x100; /* ignore ignne emulation enable */