Re: [PATCH] vhost: fix off-by-one error on nr_desc check

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Mon, Jul 25, 2016 at 04:09:58PM +0200, Maxime Coquelin wrote:
> nr_desc is not an index but the number of descriptors,
> so can be equal to the virtqueue size.
> 
> Fixes: a436f53ebfeb ("vhost: avoid dead loop chain")
> 
> Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Thanks for catching it!

> ---
> Hi Yuanhan,
> 
> I faced the bug while testing my indirect descriptor patch, it happens
> as soon as the number of chained descritors is above 2.
> 
> But the bug may in theory also be faced with normal descriptors,

In theory, yes, and only in one case, that there is a Tx has 256
descriptors chained. If that happens, I doubt things work well.
So I would say it just happens __in theory__.

> so it might
> be good to have it 16.07?

Even though, it apparently fixes a bug, so I think we could have it
for 16.07.

Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>

	--yliu