From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH 5 of 5] virtio: expose added descriptors immediately
Date: Wed, 23 Nov 2011 10:30:06 +0200
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To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christoph Hellwig <hch@infradead.org>, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization <virtualization@lists.linux-foundation.org>
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On Wed, Nov 23, 2011 at 11:49:01AM +1030, Rusty Russell wrote:
> On Tue, 22 Nov 2011 08:29:08 +0200, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> > On Tue, Nov 22, 2011 at 11:03:04AM +1030, Rusty Russell wrote:
> > > -	/* If you haven't kicked in this long, you're probably doing something
> > > -	 * wrong. */
> > > -	WARN_ON(vq->num_added > vq->vring.num);
> > > +	/* This is very unlikely, but theoretically possible.  Kick
> > > +	 * just in case. */
> > > +	if (unlikely(vq->num_added == 65535))
> > 
> > This is 0xffff but why use the decimal notation?
> 
> Interesting.  Why use hex?  Feels more like binary?

Just easier to see it's the largest 16 bit number.

> But I've changed it to "(1 << 16) - 1" to be clear.

That's even better.

> > > +		virtqueue_kick(_vq);
> > >  
> > >  	pr_debug("Added buffer head %i to %p\n", head, vq);
> > >  	END_USE(vq);
> > 
> > We also still need to reset vq->num_added, right?
> 
> virtqueue_kick does that for us.
> 
> Cheers,
> Rusty.

Right.