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>
---
v1->v2:
tweak patch description and cc:stable
---
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 5730572b52cd..54e686dca6de 100644
--- a/drivers/s390/virtio/virtio_ccw.c
+++ b/drivers/s390/virtio/virtio_ccw.c
@@ -117,7 +117,7 @@ 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;
@@ -952,7 +952,7 @@ static u8 virtio_ccw_get_status(struct virtio_device *vdev)
u8 old_status = vcdev->dma_area->status;
struct ccw1 *ccw;
- if (vcdev->revision < 1)
+ if (vcdev->revision < 2)
return vcdev->dma_area->status;
ccw = ccw_device_dma_zalloc(vcdev->cdev, sizeof(*ccw));
--
2.26.2
