On Tue, Mar 02, 2021 at 12:24:19PM +0100, Cornelia Huck wrote:
> [Backport of commit 182f709c5cff683e6732d04c78e328de0532284f to
> 4.19-stable; context diff in second hunk]
>
> CCW_CMD_READ_STATUS was introduced with revision 2 of virtio-ccw,
> and drivers should only rely on it being implemented when they
> negotiated at least that revision with the device.
>
> However, virtio_ccw_get_status() issued READ_STATUS for any
> device operating at least at revision 1. If the device accepts
> READ_STATUS regardless of the negotiated revision (which some
> implementations like QEMU do, even though the spec currently does
> not allow it), everything works as intended. While a device
> rejecting the command should also be handled gracefully, we will
> not be able to see any changes the device makes to the status,
> such as setting NEEDS_RESET or setting the status to zero after
> a completed reset.
>
> We negotiated the revision to at most 1, as we never bumped the
> maximum revision; let's do that now and properly send READ_STATUS
> only if we are operating at least at revision 2.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 7d3ce5ab9430 ("virtio/s390: support READ_STATUS command for virtio-ccw")
> Reviewed-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
> Signed-off-by: Cornelia Huck <cohuck@xxxxxxxxxx>
> Signed-off-by: Vasily Gorbik <gor@xxxxxxxxxxxxx>
> Link: https://lore.kernel.org/r/20210216110645.1087321-1-cohuck@xxxxxxxxxx
> Signed-off-by: Vasily Gorbik <gor@xxxxxxxxxxxxx>
> Signed-off-by: Cornelia Huck <cohuck@xxxxxxxxxx>
> ---
> drivers/s390/virtio/virtio_ccw.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
> index 67efdf25657f..0447ae2781ba 100644
> --- a/drivers/s390/virtio/virtio_ccw.c
> +++ b/drivers/s390/virtio/virtio_ccw.c
> @@ -103,7 +103,7 @@ struct virtio_rev_info {
> };
>
> /* the highest virtio-ccw revision we support */
> -#define VIRTIO_CCW_REV_MAX 1
> +#define VIRTIO_CCW_REV_MAX 2
>
> struct virtio_ccw_vq_info {
> struct virtqueue *vq;
> @@ -911,7 +911,7 @@ static u8 virtio_ccw_get_status(struct virtio_device *vdev)
> u8 old_status = *vcdev->status;
> struct ccw1 *ccw;
>
> - if (vcdev->revision < 1)
> + if (vcdev->revision < 2)
> return *vcdev->status;
>
> ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
> --
> 2.26.2
>
Both backports now queued up, thanks.
greg k-h
