On Tue, Feb 23, 2021 at 02:46:42PM +0000, Stefan Hajnoczi wrote:
> Treat the num_queues field as virtio-endian. On big-endian hosts the
> vhost-user-blk num_queues field was in the wrong endianness.
>
> Move the blkcfg.num_queues store operation from realize to
> vhost_user_blk_update_config() so feature negotiation has finished and
> we know the endianness of the device. VIRTIO 1.0 devices are
> little-endian, but in case someone wants to use legacy VIRTIO we support
> all endianness cases.
>
> Cc: qemu-sta...@nongnu.org
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> Reviewed-by: Raphael Norwitz <raphael.norw...@nutanix.com>
> Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
okay but as we recently discovered config space can in theory
be read before FEATURES_OK. Nasty, I know. Things kind of work
right now but we really need some other path to notify backends
when legacy guest is active. E.g. VDPA also has this problem.
> ---
> hw/block/vhost-user-blk.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
> index da4fbf9084..b870a50e6b 100644
> --- a/hw/block/vhost-user-blk.c
> +++ b/hw/block/vhost-user-blk.c
> @@ -54,6 +54,9 @@ static void vhost_user_blk_update_config(VirtIODevice
> *vdev, uint8_t *config)
> {
> VHostUserBlk *s = VHOST_USER_BLK(vdev);
>
> + /* Our num_queues overrides the device backend */
> + virtio_stw_p(vdev, &s->blkcfg.num_queues, s->num_queues);
> +
> memcpy(config, &s->blkcfg, sizeof(struct virtio_blk_config));
> }
>
> @@ -491,10 +494,6 @@ reconnect:
> goto reconnect;
> }
>
> - if (s->blkcfg.num_queues != s->num_queues) {
> - s->blkcfg.num_queues = s->num_queues;
> - }
> -
> return;
>
> virtio_err:
> --
> 2.29.2
>
