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virtio/s390: implement virtio-ccw revision 2 correctly 

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@vger.kernel.org
Fixes: 7d3ce5ab94 ("virtio/s390: support READ_STATUS command for virtio-ccw")
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Link: https://lore.kernel.org/r/20210216110645.1087321-1-cohuck@redhat.com
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Cornelia Huck 2021-02-16 12:06:45 +01:00 committed by Vasily Gorbik
parent 55f03123f6
commit 182f709c5c
1 changed files with 2 additions and 2 deletions
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4
drivers/s390/virtio/virtio_ccw.c
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@ -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));