KVM: VMX: introduce alloc_loaded_vmcs

Group together the calls to alloc_vmcs and loaded_vmcs_init.  Soon we'll also
allocate an MSR bitmap there.

Cc: stable@vger.kernel.org       # prereq for Spectre mitigation
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx.c

@@ -3829,11 +3829,6 @@ static struct vmcs *alloc_vmcs_cpu(int cpu)
 	return vmcs;
 }
 
-static struct vmcs *alloc_vmcs(void)
-{
-	return alloc_vmcs_cpu(raw_smp_processor_id());
-}
-
 static void free_vmcs(struct vmcs *vmcs)
 {
 	free_pages((unsigned long)vmcs, vmcs_config.order);
@@ -3852,6 +3847,22 @@ static void free_loaded_vmcs(struct loaded_vmcs *loaded_vmcs)
 	WARN_ON(loaded_vmcs->shadow_vmcs != NULL);
 }
 
+static struct vmcs *alloc_vmcs(void)
+{
+	return alloc_vmcs_cpu(raw_smp_processor_id());
+}
+
+static int alloc_loaded_vmcs(struct loaded_vmcs *loaded_vmcs)
+{
+	loaded_vmcs->vmcs = alloc_vmcs();
+	if (!loaded_vmcs->vmcs)
+		return -ENOMEM;
+
+	loaded_vmcs->shadow_vmcs = NULL;
+	loaded_vmcs_init(loaded_vmcs);
+	return 0;
+}
+
 static void free_kvm_area(void)
 {
 	int cpu;
@@ -7145,12 +7156,11 @@ static int enter_vmx_operation(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	struct vmcs *shadow_vmcs;
+	int r;
 
-	vmx->nested.vmcs02.vmcs = alloc_vmcs();
-	vmx->nested.vmcs02.shadow_vmcs = NULL;
-	if (!vmx->nested.vmcs02.vmcs)
+	r = alloc_loaded_vmcs(&vmx->nested.vmcs02);
+	if (r < 0)
 		goto out_vmcs02;
-	loaded_vmcs_init(&vmx->nested.vmcs02);
 
 	if (cpu_has_vmx_msr_bitmap()) {
 		vmx->nested.msr_bitmap =
@@ -9545,13 +9555,11 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
 	if (!vmx->guest_msrs)
 		goto free_pml;
 
-	vmx->loaded_vmcs = &vmx->vmcs01;
-	vmx->loaded_vmcs->vmcs = alloc_vmcs();
-	vmx->loaded_vmcs->shadow_vmcs = NULL;
-	if (!vmx->loaded_vmcs->vmcs)
+	err = alloc_loaded_vmcs(&vmx->vmcs01);
+	if (err < 0)
 		goto free_msrs;
-	loaded_vmcs_init(vmx->loaded_vmcs);
 
+	vmx->loaded_vmcs = &vmx->vmcs01;
 	cpu = get_cpu();
 	vmx_vcpu_load(&vmx->vcpu, cpu);
 	vmx->vcpu.cpu = cpu;