Re: [PATCH V5 4/6 net-next] vhost: vhost TX zero-copy support

From: Shirley Ma
Date: Tue May 17 2011 - 11:34:54 EST

On Tue, 2011-05-17 at 18:28 +0300, Michael S. Tsirkin wrote:
> Which is the order the descriptors are put on avail ring.
> By design, guest should not depend on used ring entries
> being in order with avail ring (and btw with virtio block,
> they aren't). If it does, it's a bug I think.

Ok, I thought, the order should be maintained.

> > The original code has no problem, because it gets one head and pass
> that
> > head to vhost_add_used one by one once done the copy. So it's in
> > sequence.
> >
> > This issue can easily recreate without zerocopy patch by simply
> changing
> > the order from "head return vhost_get_vq_desc" when passing to
> > vhost_add_used.
> >
> > Thanks
> > Shirley
> Ah, did you try that? Could you post this patch pls?
> This seems to imply a bug in guest virtio.

I am creating the patch against net-next for you to test today.


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