Re: [PATCH] vhost: fix initialization for vq->is_le

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jan 31, 2017 at 04:56:13PM +0100, Halil Pasic wrote:
> 
> 
> On 01/30/2017 08:06 PM, Greg Kurz wrote:
> >> Currently, under certain circumstances vhost_init_is_le does just a part
> >> of the initialization job, and depends on vhost_reset_is_le being called
> >> too. For this reason vhost_vq_init_access used to call vhost_reset_is_le
> >> when vq->private_data is NULL. This is not only counter intuitive, but
> >> also real a problem because it breaks vhost_net. The bug was introduced to
> >> vhost_net with commit 2751c9882b94 ("vhost: cross-endian support for
> >> legacy devices"). The symptom is corruption of the vq's used.idx field
> >> (virtio) after VHOST_NET_SET_BACKEND was issued as a part of the vhost
> >> shutdown on a vq with pending descriptors.
> >>
> >> Let us make sure the outcome of vhost_init_is_le never depend on the state
> >> it is actually supposed to initialize, and fix virtio_net by removing the
> >> reset from vhost_vq_init_access.
> >>
> >> With the above, there is no reason for vhost_reset_is_le to do just half
> >> of the job. Let us make vhost_reset_is_le reinitialize is_le.
> >>
> >> Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
> >> Reported-by: Michael A. Tebolt <miket@us.ibm.com>
> >> Reported-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> >> Fixes: commit 2751c9882b94 ("vhost: cross-endian support for legacy devices")
> >> ---
> > Reviewed-by: Greg Kurz <groug@kaod.org>
> > 
> 
> Thanks! 
> 
> We have some tests on s390x (that is BE) running, but I won't be able to
> test the change with cross endian and legacy. 
> 
> What do you think, should I/we RFT or are we fine without?
> 
> Regards,
> Halil

More testing can't hurt. I can merge this meanwhile.

-- 
MST