KVM: selftests: Return the created vCPU from vm_vcpu_add()

Return the created vCPU from vm_vcpu_add() so that callers don't need to
manually retrieve the vCPU that was just added.  Opportunistically drop
the "heavy" function comment, it adds a lot of lines of "code" but not
much value, e.g. it's pretty obvious that @vm is a virtual machine...
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/include/kvm_util_base.h

@@ -324,7 +324,7 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
 void vm_mem_region_set_flags(struct kvm_vm *vm, uint32_t slot, uint32_t flags);
 void vm_mem_region_move(struct kvm_vm *vm, uint32_t slot, uint64_t new_gpa);
 void vm_mem_region_delete(struct kvm_vm *vm, uint32_t slot);
-void vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpuid);
+struct kvm_vcpu *vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpuid);
 vm_vaddr_t vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min);
 vm_vaddr_t vm_vaddr_alloc_pages(struct kvm_vm *vm, int nr_pages);
 vm_vaddr_t vm_vaddr_alloc_page(struct kvm_vm *vm);

tools/testing/selftests/kvm/lib/kvm_util.c

@@ -397,8 +397,7 @@ struct kvm_vcpu *vm_recreate_with_one_vcpu(struct kvm_vm *vm)
 {
 	kvm_vm_restart(vm);
 
-	vm_vcpu_add(vm, 0);
-	return vcpu_get(vm, 0);
+	return vm_vcpu_add(vm, 0);
 }
 
 /*
@@ -1063,33 +1062,23 @@ static int vcpu_mmap_sz(void)
 }
 
 /*
- * VM VCPU Add
- *
- * Input Args:
- *   vm - Virtual Machine
- *   vcpuid - VCPU ID
- *
- * Output Args: None
- *
- * Return: None
- *
- * Adds a virtual CPU to the VM specified by vm with the ID given by vcpuid.
- * No additional VCPU setup is done.
+ * Adds a virtual CPU to the VM specified by vm with the ID given by vcpu_id.
+ * No additional vCPU setup is done.  Returns the vCPU.
  */
-void vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpuid)
+struct kvm_vcpu *vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
 {
 	struct kvm_vcpu *vcpu;
 
 	/* Confirm a vcpu with the specified id doesn't already exist. */
-	TEST_ASSERT(!vcpu_find(vm, vcpuid), "vCPU%d already exists\n", vcpuid);
+	TEST_ASSERT(!vcpu_find(vm, vcpu_id), "vCPU%d already exists\n", vcpu_id);
 
 	/* Allocate and initialize new vcpu structure. */
 	vcpu = calloc(1, sizeof(*vcpu));
 	TEST_ASSERT(vcpu != NULL, "Insufficient Memory");
 
 	vcpu->vm = vm;
-	vcpu->id = vcpuid;
-	vcpu->fd = __vm_ioctl(vm, KVM_CREATE_VCPU, (void *)(unsigned long)vcpuid);
+	vcpu->id = vcpu_id;
+	vcpu->fd = __vm_ioctl(vm, KVM_CREATE_VCPU, (void *)(unsigned long)vcpu_id);
 	TEST_ASSERT(vcpu->fd >= 0, KVM_IOCTL_ERROR(KVM_CREATE_VCPU, vcpu->fd));
 
 	TEST_ASSERT(vcpu_mmap_sz() >= sizeof(*vcpu->run), "vcpu mmap size "
@@ -1102,6 +1091,8 @@ void vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpuid)
 
 	/* Add to linked-list of VCPUs. */
 	list_add(&vcpu->list, &vm->vcpus);
+
+	return vcpu;
 }
 
 /*