KVM: nSVM: Restore nested control upon leaving SMM

If the VM was migrated while in SMM, no nested state was saved/restored,
and therefore svm_leave_smm has to load both save and control area
of the vmcb12. Save area is already loaded from HSAVE area,
so now load the control area as well from the vmcb12.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210628104425.391276-6-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/nested.c

@@ -308,7 +308,7 @@ static bool nested_vmcb_valid_sregs(struct kvm_vcpu *vcpu,
 	return true;
 }
 
-static void nested_load_control_from_vmcb12(struct vcpu_svm *svm,
+void nested_load_control_from_vmcb12(struct vcpu_svm *svm,
 				     struct vmcb_control_area *control)
 {
 	copy_vmcb_control_area(&svm->nested.ctl, control);

arch/x86/kvm/svm/svm.c

@@ -4362,6 +4362,7 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
 		u64 saved_efer = GET_SMSTATE(u64, smstate, 0x7ed0);
 		u64 guest = GET_SMSTATE(u64, smstate, 0x7ed8);
 		u64 vmcb12_gpa = GET_SMSTATE(u64, smstate, 0x7ee0);
+		struct vmcb *vmcb12;
 
 		if (guest) {
 			if (!guest_cpuid_has(vcpu, X86_FEATURE_SVM))
@@ -4377,7 +4378,11 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
 			if (svm_allocate_nested(svm))
 				return 1;
 
-			ret = enter_svm_guest_mode(vcpu, vmcb12_gpa, map.hva);
+			vmcb12 = map.hva;
+
+			nested_load_control_from_vmcb12(svm, &vmcb12->control);
+
+			ret = enter_svm_guest_mode(vcpu, vmcb12_gpa, vmcb12);
 			kvm_vcpu_unmap(vcpu, &map, true);
 
 			/*

arch/x86/kvm/svm/svm.h

@@ -482,6 +482,8 @@ int nested_svm_check_permissions(struct kvm_vcpu *vcpu);
 int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
 			       bool has_error_code, u32 error_code);
 int nested_svm_exit_special(struct vcpu_svm *svm);
+void nested_load_control_from_vmcb12(struct vcpu_svm *svm,
+				     struct vmcb_control_area *control);
 void nested_sync_control_from_vmcb02(struct vcpu_svm *svm);
 void nested_vmcb02_compute_g_pat(struct vcpu_svm *svm);
 void svm_switch_vmcb(struct vcpu_svm *svm, struct kvm_vmcb_info *target_vmcb);