KVM: Fix mov cr3 #GP at wrong instruction

On Intel, we call skip_emulated_instruction() even if we injected a #GP,
resulting in the #GP pointing at the wrong address.

Fix by injecting the exception and skipping the instruction at the same place,
so we can do just one or the other.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -598,7 +598,7 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int reason,
 		    bool has_error_code, u32 error_code);
 
 int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
-void kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3);
+int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3);
 int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
 void kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8);
 int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val);

arch/x86/kvm/mmu.c

@@ -3203,7 +3203,7 @@ static int kvm_pv_mmu_write(struct kvm_vcpu *vcpu,
 
 static int kvm_pv_mmu_flush_tlb(struct kvm_vcpu *vcpu)
 {
-	kvm_set_cr3(vcpu, vcpu->arch.cr3);
+	(void)kvm_set_cr3(vcpu, vcpu->arch.cr3);
 	return 1;
 }
 

arch/x86/kvm/svm.c

@@ -1963,7 +1963,7 @@ static int nested_svm_vmexit(struct vcpu_svm *svm)
 		svm->vmcb->save.cr3 = hsave->save.cr3;
 		svm->vcpu.arch.cr3 = hsave->save.cr3;
 	} else {
-		kvm_set_cr3(&svm->vcpu, hsave->save.cr3);
+		(void)kvm_set_cr3(&svm->vcpu, hsave->save.cr3);
 	}
 	kvm_register_write(&svm->vcpu, VCPU_REGS_RAX, hsave->save.rax);
 	kvm_register_write(&svm->vcpu, VCPU_REGS_RSP, hsave->save.rsp);
@@ -2086,7 +2086,7 @@ static bool nested_svm_vmrun(struct vcpu_svm *svm)
 		svm->vmcb->save.cr3 = nested_vmcb->save.cr3;
 		svm->vcpu.arch.cr3 = nested_vmcb->save.cr3;
 	} else
-		kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3);
+		(void)kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3);
 
 	/* Guest paging mode is active - reset mmu */
 	kvm_mmu_reset_context(&svm->vcpu);

arch/x86/kvm/vmx.c

@@ -3185,8 +3185,8 @@ static int handle_cr(struct kvm_vcpu *vcpu)
 			complete_insn_gp(vcpu, err);
 			return 1;
 		case 3:
-			kvm_set_cr3(vcpu, val);
-			skip_emulated_instruction(vcpu);
+			err = kvm_set_cr3(vcpu, val);
+			complete_insn_gp(vcpu, err);
 			return 1;
 		case 4:
 			err = kvm_set_cr4(vcpu, val);

arch/x86/kvm/x86.c

@@ -565,7 +565,7 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 }
 EXPORT_SYMBOL_GPL(kvm_set_cr4);
 
-static int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
+int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 {
 	if (cr3 == vcpu->arch.cr3 && !pdptrs_changed(vcpu)) {
 		kvm_mmu_sync_roots(vcpu);
@@ -604,12 +604,6 @@ static int __kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 	vcpu->arch.mmu.new_cr3(vcpu);
 	return 0;
 }
-
-void kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
-{
-	if (__kvm_set_cr3(vcpu, cr3))
-		kvm_inject_gp(vcpu, 0);
-}
 EXPORT_SYMBOL_GPL(kvm_set_cr3);
 
 int __kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8)
@@ -3726,7 +3720,7 @@ static int emulator_set_cr(int cr, unsigned long val, struct kvm_vcpu *vcpu)
 		vcpu->arch.cr2 = val;
 		break;
 	case 3:
-		res = __kvm_set_cr3(vcpu, val);
+		res = kvm_set_cr3(vcpu, val);
 		break;
 	case 4:
 		res = kvm_set_cr4(vcpu, mk_cr_64(kvm_read_cr4(vcpu), val));