On Tue, 31 Jan 2017 16:56:13 +0100
Halil Pasic [off-list ref] wrote:

On 01/30/2017 08:06 PM, Greg Kurz wrote:

quoted

quoted

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 <redacted>
Reported-by: Michael A. Tebolt <redacted>
Reported-by: Dr. David Alan Gilbert <redacted>
Fixes: commit 2751c9882b94 ("vhost: cross-endian support for legacy devices")
---  

Reviewed-by: Greg Kurz <redacted>
  

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. 

I'll try to find some time to run such tests on ppc.

Cheers.

--
Greg

What do you think, should I/we RFT or are we fine without?

Regards,
Halil