On Mon, Jul 15, 2024 at 11:45 AM Zhao Liu <zhao1....@intel.com> wrote:
>
> As the comment in qapi/error, dereferencing @errp requires
> ERRP_GUARD():
>
> * = Why, when and how to use ERRP_GUARD() =
> *
> * Without ERRP_GUARD(), use of the @errp parameter is restricted:
> * - It must not be dereferenced, because it may be null.
> ...
> * ERRP_GUARD() lifts these restrictions.
> *
> * To use ERRP_GUARD(), add it right at the beginning of the function.
> * @errp can then be used without worrying about the argument being
> * NULL or &error_fatal.
> *
> * Using it when it's not needed is safe, but please avoid cluttering
> * the source with useless code.
>
> Though vhost_vdpa_device_realize() is called at DeviceClass.realize()
> context and won't get NULL @errp, it's still better to follow the
> requirement to add the ERRP_GUARD().
>
> But qemu_open() and vhost_vdpa_device_get_u32()'s return values can
> distinguish between successful and unsuccessful calls, so check the
> return values directly without dereferencing @errp, which eliminates
> the need of ERRP_GUARD().
>
> Cc: "Michael S. Tsirkin" <m...@redhat.com>
> Cc: "Eugenio Pérez" <epere...@redhat.com>
> Cc: Jason Wang <jasow...@redhat.com>
> Signed-off-by: Zhao Liu <zhao1....@intel.com>
> ---
> hw/virtio/vdpa-dev.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/hw/virtio/vdpa-dev.c b/hw/virtio/vdpa-dev.c
> index 64b96b226c39..7b439efdc1d3 100644
> --- a/hw/virtio/vdpa-dev.c
> +++ b/hw/virtio/vdpa-dev.c
> @@ -50,6 +50,7 @@ vhost_vdpa_device_get_u32(int fd, unsigned long int cmd,
> Error **errp)
>
> static void vhost_vdpa_device_realize(DeviceState *dev, Error **errp)
> {
> + ERRP_GUARD();
Good catch, thank you! But removing the err dereferencing eliminates
the need for ERRP_GUARD(), doesn't it?
Thanks!
> VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> VhostVdpaDevice *v = VHOST_VDPA_DEVICE(vdev);
> struct vhost_vdpa_iova_range iova_range;
> @@ -63,19 +64,19 @@ static void vhost_vdpa_device_realize(DeviceState *dev,
> Error **errp)
> }
>
> v->vhostfd = qemu_open(v->vhostdev, O_RDWR, errp);
> - if (*errp) {
> + if (v->vhostfd < 0) {
> return;
> }
>
> v->vdev_id = vhost_vdpa_device_get_u32(v->vhostfd,
> VHOST_VDPA_GET_DEVICE_ID, errp);
> - if (*errp) {
> + if (v->vdev_id < 0) {
> goto out;
> }
>
> max_queue_size = vhost_vdpa_device_get_u32(v->vhostfd,
> VHOST_VDPA_GET_VRING_NUM,
> errp);
> - if (*errp) {
> + if (max_queue_size < 0) {
> goto out;
> }
>
> @@ -89,7 +90,7 @@ static void vhost_vdpa_device_realize(DeviceState *dev,
> Error **errp)
>
> v->num_queues = vhost_vdpa_device_get_u32(v->vhostfd,
> VHOST_VDPA_GET_VQS_COUNT,
> errp);
> - if (*errp) {
> + if (v->num_queues < 0) {
> goto out;
> }
>
> @@ -127,7 +128,7 @@ static void vhost_vdpa_device_realize(DeviceState *dev,
> Error **errp)
> v->config_size = vhost_vdpa_device_get_u32(v->vhostfd,
> VHOST_VDPA_GET_CONFIG_SIZE,
> errp);
> - if (*errp) {
> + if (v->config_size < 0) {
> goto vhost_cleanup;
> }
>
> --
> 2.34.1
>
