[4.19,04/52] virtio/s390: implement virtio-ccw revision 2 correctly
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Message ID 20210305120853.878276639@linuxfoundation.org
State New, archived
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  • Untitled series #487861
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Commit Message

Greg KH March 5, 2021, 12:21 p.m. UTC
From: Cornelia Huck <cohuck@redhat.com>

commit 182f709c5cff683e6732d04c78e328de0532284f upstream.

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: 7d3ce5ab9430 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

 drivers/s390/virtio/virtio_ccw.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

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--- 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 */
 struct virtio_ccw_vq_info {
 	struct virtqueue *vq;
@@ -911,7 +911,7 @@  static u8 virtio_ccw_get_status(struct v
 	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);