KVM: SVM: Activate nested state only when guest state is complete

Certain functions called during the emulated world switch
behave differently when the vcpu is running nested. This is
not the expected behavior during a world switch emulation.
This patch ensures that the nested state is activated only
if the vcpu is completly in nested state.
Signed-off-by: NJoerg Roedel <joerg.roedel@amd.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

arch/x86/kvm/svm.c

@@ -1633,6 +1633,9 @@ static int nested_svm_vmexit(struct vcpu_svm *svm)
 	if (!nested_vmcb)
 		return 1;
 
+	/* Exit nested SVM mode */
+	svm->nested.vmcb = 0;
+
 	/* Give the current vmcb to the guest */
 	disable_gif(svm);
 
@@ -1720,9 +1723,6 @@ static int nested_svm_vmexit(struct vcpu_svm *svm)
 	svm->vmcb->save.cpl = 0;
 	svm->vmcb->control.exit_int_info = 0;
 
-	/* Exit nested SVM mode */
-	svm->nested.vmcb = 0;
-
 	nested_svm_unmap(page);
 
 	kvm_mmu_reset_context(&svm->vcpu);
@@ -1757,14 +1757,14 @@ static bool nested_svm_vmrun(struct vcpu_svm *svm)
 	struct vmcb *hsave = svm->nested.hsave;
 	struct vmcb *vmcb = svm->vmcb;
 	struct page *page;
+	u64 vmcb_gpa;
+
+	vmcb_gpa = svm->vmcb->save.rax;
 
 	nested_vmcb = nested_svm_map(svm, svm->vmcb->save.rax, &page);
 	if (!nested_vmcb)
 		return false;
 
-	/* nested_vmcb is our indicator if nested SVM is activated */
-	svm->nested.vmcb = svm->vmcb->save.rax;
-
 	trace_kvm_nested_vmrun(svm->vmcb->save.rip - 3, svm->nested.vmcb,
 			       nested_vmcb->save.rip,
 			       nested_vmcb->control.int_ctl,
@@ -1879,6 +1879,9 @@ static bool nested_svm_vmrun(struct vcpu_svm *svm)
 
 	nested_svm_unmap(page);
 
+	/* nested_vmcb is our indicator if nested SVM is activated */
+	svm->nested.vmcb = vmcb_gpa;
+
 	enable_gif(svm);
 
 	return true;