Re: [RFC v3 4/6] qmp: add QMP command x-debug-virtio-queue-status

[Jason Wang]

On 2020/5/15 下午11:16, Laurent Vivier wrote:
> On 08/05/2020 04:57, Jason Wang wrote:
> > On 2020/5/7 下午7:49, Laurent Vivier wrote:
> > > This new command shows internal status of a VirtQueue.
> > > (vrings and indexes).
> > >
> > > Signed-off-by: Laurent Vivier <address@hidden>
> >
> > It looks to me that packed virtqueue is not supported. It's better to
> > add them in the future.
> I agree, it's why the series still remains an "RFC".
>
> ...
> > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> > > index 59bf6ef651a6..57552bf05014 100644
> > > --- a/hw/virtio/virtio.c
> > > +++ b/hw/virtio/virtio.c
> > > @@ -3877,6 +3877,41 @@ static VirtIODevice *virtio_device_find(const
> > > char *path)
> > >        return NULL;
> > >    }
> > >    +VirtQueueStatus *qmp_x_debug_virtio_queue_status(const char *path,
> > > +                                                 uint16_t queue,
> > > Error **errp)
> > > +{
> > > +    VirtIODevice *vdev;
> > > +    VirtQueueStatus *status;
> > > +
> > > +    vdev = virtio_device_find(path);
> > > +    if (vdev == NULL) {
> > > +        error_setg(errp, "Path %s is not a VirtIO device", path);
> > > +        return NULL;
> > > +    }
> > > +
> > > +    if (queue >= VIRTIO_QUEUE_MAX || !virtio_queue_get_num(vdev,
> > > queue)) {
> > > +        error_setg(errp, "Invalid virtqueue number %d", queue);
> > > +        return NULL;
> > > +    }
> > > +
> > > +    status = g_new0(VirtQueueStatus, 1);
> > > +    status->queue_index = vdev->vq[queue].queue_index;
> > > +    status->inuse = vdev->vq[queue].inuse;
> > > +    status->vring_num = vdev->vq[queue].vring.num;
> > > +    status->vring_num_default = vdev->vq[queue].vring.num_default;
> > > +    status->vring_align = vdev->vq[queue].vring.align;
> > > +    status->vring_desc = vdev->vq[queue].vring.desc;
> > > +    status->vring_avail = vdev->vq[queue].vring.avail;
> > > +    status->vring_used = vdev->vq[queue].vring.used;
> > > +    status->last_avail_idx = vdev->vq[queue].last_avail_idx;
> >
> > This might not be correct when vhost is used.
> >
> > We may consider to sync last_avail_idx from vhost backends here?
> Yes, but I don't know how to do that. Where can I find the information?


It could be synced through vhost ops vhost_get_vring_base(), see 
vhost_virtqueue_stop().

Thanks


> Thanks,
> Laurent