[SeaBIOS] [PATCH] fix two issues with virtio-blk

[Gleb Natapov]

On Wed, May 12, 2010 at 04:42:30PM +0100, Stefan Hajnoczi wrote:
> On Tue, May 11, 2010 at 1:21 PM, Gleb Natapov <gleb at redhat.com> wrote:
> > 2. Disable interrupt otherwise interrupt may stuck
> >   with some guests.
> [...]
> > diff --git a/src/virtio-ring.h b/src/virtio-ring.h
> > index 95ae85b..f2f2460 100644
> > --- a/src/virtio-ring.h
> > +++ b/src/virtio-ring.h
> > @@ -105,6 +105,8 @@ static inline void vring_init(struct vring *vr,
> >    vr->desc = phys_to_virt(pa);
> >
> >    vr->avail = (struct vring_avail *)&vr->desc[num];
> > +   /* disable interrupts */
> > +   vr->avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
> 
> I don't understand this.  Why would the interrupt get stuck?
> 
Because virtio-blk will send interrupt on read completion, but nobody
ever clears it and if OS will unmask the interrupt before virtio-blk
initialization nobody will know how to ack it.

> The virtio-net device closely manages interrupts because it uses NAPI.
>  The virtio-blk device assumes it will receive interrupts and doesn't
> enable_cb/disable_cb.  I might be confused but have you tested this
> change with virtio-blk?
>
This is per virt queue flag. virtio-blk creates another virt queue
without the flag. It works for me with virtio-blk.

--
			Gleb.