Re: [PATCH v2] hw/virtio/vdpa-dev: Check returned value instead of dereferencing @errp

[Zhao Liu <zhao1.liu@intel.com>]

Hi Michael,

On Tue, Aug 20, 2024 at 06:55:29AM -0400, Michael S. Tsirkin wrote:

[snip]

> > diff --git a/hw/virtio/vdpa-dev.c b/hw/virtio/vdpa-dev.c
> > index 64b96b226c39..8a1e16fce3de 100644
> > --- a/hw/virtio/vdpa-dev.c
> > +++ b/hw/virtio/vdpa-dev.c
> > @@ -63,19 +63,19 @@ 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;
> >      }
> 
> vdev_id is unsigned, no idea how is this supposed to work.
> 
> >  
> >      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;
> >      }
> >  
> max_queue_size is unsigned, too.
> 
> > @@ -89,7 +89,7 @@ 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;
> >      }
> >  
> 
> num_queues is unsigned, too.

Oops, yes. The correct way is to check whether vhost_vdpa_device_get_u32
returns "(uint32_t)-1".

I can add a new macro like this:

#define VDPA_DEVICE_U32_VALUE_NONE ((uint32_t)-1)

Is this okay with you?

Thanks,
Zhao

> > @@ -127,7 +127,7 @@ 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
>