KVM: nSVM: use vmcb_save_area_cached in nested_vmcb_valid_sregs()

Now that struct vmcb_save_area_cached contains the required
vmcb fields values (done in nested_load_save_from_vmcb12()),
check them to see if they are correct in nested_vmcb_valid_sregs().

While at it, rename nested_vmcb_valid_sregs in nested_vmcb_check_save.
__nested_vmcb_check_save takes the additional @save parameter, so it
is helpful when we want to check a non-svm save state, like in
svm_set_nested_state. The reason for that is that save is the L1
state, not L2, so we check it without moving it to svm->nested.save.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20211103140527.752797-5-eesposit@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/nested.c

@@ -245,8 +245,8 @@ static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
 }
 
 /* Common checks that apply to both L1 and L2 state.  */
-static bool nested_vmcb_valid_sregs(struct kvm_vcpu *vcpu,
-				    struct vmcb_save_area *save)
+static bool __nested_vmcb_check_save(struct kvm_vcpu *vcpu,
+				     struct vmcb_save_area_cached *save)
 {
 	/*
 	 * FIXME: these should be done after copying the fields,
@@ -286,6 +286,14 @@ static bool nested_vmcb_valid_sregs(struct kvm_vcpu *vcpu,
 	return true;
 }
 
+static bool nested_vmcb_check_save(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+	struct vmcb_save_area_cached *save = &svm->nested.save;
+
+	return __nested_vmcb_check_save(vcpu, save);
+}
+
 static
 void __nested_copy_vmcb_control_to_cache(struct vmcb_control_area *to,
 					 struct vmcb_control_area *from)
@@ -694,7 +702,7 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
 	nested_copy_vmcb_control_to_cache(svm, &vmcb12->control);
 	nested_copy_vmcb_save_to_cache(svm, &vmcb12->save);
 
-	if (!nested_vmcb_valid_sregs(vcpu, &vmcb12->save) ||
+	if (!nested_vmcb_check_save(vcpu) ||
 	    !nested_vmcb_check_controls(vcpu, &svm->nested.ctl)) {
 		vmcb12->control.exit_code    = SVM_EXIT_ERR;
 		vmcb12->control.exit_code_hi = 0;
@@ -1330,6 +1338,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
 		&user_kvm_nested_state->data.svm[0];
 	struct vmcb_control_area *ctl;
 	struct vmcb_save_area *save;
+	struct vmcb_save_area_cached save_cached;
 	unsigned long cr0;
 	int ret;
 
@@ -1397,10 +1406,11 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
 	 * Validate host state saved from before VMRUN (see
 	 * nested_svm_check_permissions).
 	 */
+	__nested_copy_vmcb_save_to_cache(&save_cached, save);
 	if (!(save->cr0 & X86_CR0_PG) ||
 	    !(save->cr0 & X86_CR0_PE) ||
 	    (save->rflags & X86_EFLAGS_VM) ||
-	    !nested_vmcb_valid_sregs(vcpu, save))
+	    !__nested_vmcb_check_save(vcpu, &save_cached))
 		goto out_free;
 
 	/*