Re: [PATCH v2 07/24] virtio-pci: support queue enable

[Jason Wang]

在 2022/8/23 16:20, Kangjie Xu 写道:
> 在 2022/8/23 15:44, Jason Wang 写道:
> > 在 2022/8/16 09:06, Kangjie Xu 写道:
> > > PCI devices support vq enable.
> >
> >
> > Nit: it might be "support device specific vq enable"
> Get it.
> > > Based on this function, the driver can re-enable the virtqueue after 
> > > the
> > > virtqueue is reset.
> > >
> > > Signed-off-by: Kangjie Xu <kangjie.xu@linux.alibaba.com>
> > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > > ---
> > >   hw/virtio/virtio-pci.c | 1 +
> > >   1 file changed, 1 insertion(+)
> > >
> > > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > > index ec8e92052f..3d560e45ad 100644
> > > --- a/hw/virtio/virtio-pci.c
> > > +++ b/hw/virtio/virtio-pci.c
> > > @@ -1335,6 +1335,7 @@ static void virtio_pci_common_write(void 
> > > *opaque, hwaddr addr,
> > > proxy->vqs[vdev->queue_sel].avail[0],
> > > ((uint64_t)proxy->vqs[vdev->queue_sel].used[1]) << 32 |
> > > proxy->vqs[vdev->queue_sel].used[0]);
> > > +            virtio_queue_enable(vdev, vdev->queue_sel);
> > >               proxy->vqs[vdev->queue_sel].enabled = 1;
> > >               proxy->vqs[vdev->queue_sel].reset = 0;
> >
> >
> > Any reason we do it before the assignment of 1? It probably means the 
> > device specific method can't depend on virtio_queue_enabled()?
> >
> > Thanks
> Sorry, I don't get why device specific method can't depend on 
> virtio_queue_enabled().


I meant if the device specific method call virtio_queue_enabled() it 
will return false in this case, is this intended?


> Before virtio_queue_enable() is done, virtqueue should always be not 
> ready and disabled.
>
> Otherwise, If we put it after the assignment of enabled to 1, the 
> virtqueue may be accessed illegally and may cause panic, because the 
> virtqueue is still being intialized and being configured.


How? Shouldn't we make transport ready before making device 
virtqueue(device) ready?

Thanks


> Thanks
>
> > >           } else {