KVM: x86: Inject #GP with the right rip on efer writes

This patch fixes a bug in the KVM efer-msr write path. If a
guest writes to a reserved efer bit the set_efer function
injects the #GP directly. The architecture dependent wrmsr
function does not see this, assumes success and advances the
rip. This results in a #GP in the guest with the wrong rip.
This patch fixes this by reporting efer write errors back to
the architectural wrmsr function.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 12 insertions, 19 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 161ede2b5f91..fe6d126633d8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -683,37 +683,29 @@ static u32 emulated_msrs[] = {
         MSR_IA32_MISC_ENABLE,
 };
 
-static void set_efer(struct kvm_vcpu *vcpu, u64 efer)
+static int set_efer(struct kvm_vcpu *vcpu, u64 efer)
 {
-        if (efer & efer_reserved_bits) {
-                kvm_inject_gp(vcpu, 0);
-                return;
-        }
+        if (efer & efer_reserved_bits)
+                return 1;
 
         if (is_paging(vcpu)
-            && (vcpu->arch.efer & EFER_LME) != (efer & EFER_LME)) {
-                kvm_inject_gp(vcpu, 0);
-                return;
-        }
+            && (vcpu->arch.efer & EFER_LME) != (efer & EFER_LME))
+                return 1;
 
         if (efer & EFER_FFXSR) {
                 struct kvm_cpuid_entry2 *feat;
 
                 feat = kvm_find_cpuid_entry(vcpu, 0x80000001, 0);
-                if (!feat || !(feat->edx & bit(X86_FEATURE_FXSR_OPT))) {
-                        kvm_inject_gp(vcpu, 0);
-                        return;
-                }
+                if (!feat || !(feat->edx & bit(X86_FEATURE_FXSR_OPT)))
+                        return 1;
         }
 
         if (efer & EFER_SVME) {
                 struct kvm_cpuid_entry2 *feat;
 
                 feat = kvm_find_cpuid_entry(vcpu, 0x80000001, 0);
-                if (!feat || !(feat->ecx & bit(X86_FEATURE_SVM))) {
-                        kvm_inject_gp(vcpu, 0);
-                        return;
-                }
+                if (!feat || !(feat->ecx & bit(X86_FEATURE_SVM)))
+                        return 1;
         }
 
         kvm_x86_ops->set_efer(vcpu, efer);
@@ -725,6 +717,8 @@ static void set_efer(struct kvm_vcpu *vcpu, u64 efer)
 
         vcpu->arch.mmu.base_role.nxe = (efer & EFER_NX) && !tdp_enabled;
         kvm_mmu_reset_context(vcpu);
+
+        return 0;
 }
 
 void kvm_enable_efer_bits(u64 mask)
@@ -1153,8 +1147,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 {
         switch (msr) {
         case MSR_EFER:
-                set_efer(vcpu, data);
-                break;
+                return set_efer(vcpu, data);
         case MSR_K7_HWCR:
                 data &= ~(u64)0x40;     /* ignore flush filter disable */
                 data &= ~(u64)0x100;    /* ignore ignne emulation enable */