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authorSean Christopherson <sean.j.christopherson@intel.com>2019-04-02 08:19:15 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-05-21 18:49:01 +0200
commit0dd8bef58e0bd262962d9a2f4d42f670d64f9e44 (patch)
treea232786b5ff6d5b87d1c5c50f234287cda8977d6
parent51776204959bd7c1db0f76b8d1a3bccf9411abc1 (diff)
KVM: x86: Skip EFER vs. guest CPUID checks for host-initiated writes
commit 11988499e62b310f3bf6f6d0a807a06d3f9ccc96 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/x86/kvm/x86.c33
1 files changed, 22 insertions, 11 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8285142556b5..1f32c4e32a00 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1073,11 +1073,8 @@ 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) {
struct kvm_cpuid_entry2 *feat;
@@ -1095,19 +1092,33 @@ bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer)
}
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;
@@ -2203,7 +2214,7 @@ 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 */