Re: [PATCH v1 1/2] virtio: struct VirtQueue introduce reset

[Xuan Zhuo]

On Sun, 29 Jan 2023 02:12:36 -0500, "Michael S. Tsirkin" <mst@redhat.com> wrote:
>
> subject seems wrong.


Will fix.


>
> On Sun, Jan 29, 2023 at 10:51:49AM +0800, Xuan Zhuo wrote:
> > In the current design, we stop the device from operating on the vring
> > during per-queue reset by resetting the structure VirtQueue.
> >
> > But before the reset operation, when recycling some resources, we should
> > stop referencing new vring resources. For example, when recycling
> > virtio-net's asynchronous sending resources, virtio-net should be able
> > to perceive that the current queue is in the per-queue reset state, and
> > stop sending new packets from the tx queue.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > ---
> >  hw/virtio/virtio.c         | 15 +++++++++++++++
> >  include/hw/virtio/virtio.h |  1 +
> >  2 files changed, 16 insertions(+)
> >
> > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> > index f35178f5fc..c954f2a2b3 100644
> > --- a/hw/virtio/virtio.c
> > +++ b/hw/virtio/virtio.c
> > @@ -142,6 +142,8 @@ struct VirtQueue
> >      /* Notification enabled? */
> >      bool notification;
> >
> > +    bool disabled_by_reset;
> > +
> >      uint16_t queue_index;
> >
> >      unsigned int inuse;
> > @@ -2079,6 +2081,12 @@ void virtio_queue_reset(VirtIODevice *vdev, uint32_t 
> > queue_index)
> >  {
> >      VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> >
> > +    /*
> > +     * Mark this queue is per-queue reset status. The device should 
> > release the
> > +     * references of the vring, and not refer more new vring item.
>
> items


Will fix.

>
> > +     */
> > +    vdev->vq[queue_index].disabled_by_reset = true;
> > +
> >      if (k->queue_reset) {
> >          k->queue_reset(vdev, queue_index);
> >      }
>
> can we set this after calling queue_reset? For symmetry with enable.


In fact,  queue_reset() will check it.


>
> > @@ -2102,11 +2110,18 @@ void virtio_queue_enable(VirtIODevice *vdev, 
> > uint32_t queue_index)
> >      }
> >      */
> >
> > +    vdev->vq[queue_index].disabled_by_reset = false;
> > +
> >      if (k->queue_enable) {
> >          k->queue_enable(vdev, queue_index);
> >      }
> >  }
> >
> > +bool virtio_queue_reset_state(VirtQueue *vq)
> > +{
> > +    return vq->disabled_by_reset;
> > +}
> > +
> >  void virtio_reset(void *opaque)
> >  {
> >      VirtIODevice *vdev = opaque;
> > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> > index 77c6c55929..00e91af7c4 100644
> > --- a/include/hw/virtio/virtio.h
> > +++ b/include/hw/virtio/virtio.h
> > @@ -319,6 +319,7 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val);
> >  void virtio_reset(void *opaque);
> >  void virtio_queue_reset(VirtIODevice *vdev, uint32_t queue_index);
> >  void virtio_queue_enable(VirtIODevice *vdev, uint32_t queue_index);
> > +bool virtio_queue_reset_state(VirtQueue *vq);
> >  void virtio_update_irq(VirtIODevice *vdev);
> >  int virtio_set_features(VirtIODevice *vdev, uint64_t val);
>
> OK I guess ... what about migration. This state won't be
> set correctly will it?

I think it has no effect. After the reset, there is actually no state. We can
migrate.

The current variable is only used by ->queue_reset().

Thanks.


>
>
> >
> > --
> > 2.32.0.3.g01195cf9f
>