vfio: ccw: introduce support for ccw0

Although Linux does not use format-0 channel command words (CCW0)
these are a non-optional part of the platform spec, and for the sake
of platform compliance, and possibly some non-Linux guests, we have
to support CCW0.

Making the kernel execute a format 0 channel program is too much hassle
because we would need to allocate and use memory which can be addressed
by 24 bit physical addresses (because of CCW0.cda). So we implement CCW0
support by translating the channel program into an equivalent CCW1
program instead.

Based upon an orginal patch by Kai Yue Wang.
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Message-Id: <20170317031743.40128-16-bjsdjshi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

1 files changed, 29 insertions, 3 deletions

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index 16bbb54ee532..ba6ac83a6c25 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -247,7 +247,34 @@ static long copy_ccw_from_iova(struct channel_program *cp,
 			       struct ccw1 *to, u64 iova,
 			       unsigned long len)
 {
-	return copy_from_iova(cp->mdev, to, iova, len * sizeof(struct ccw1));
+	struct ccw0 ccw0;
+	struct ccw1 *pccw1;
+	int ret;
+	int i;
+
+	ret = copy_from_iova(cp->mdev, to, iova, len * sizeof(struct ccw1));
+	if (ret)
+		return ret;
+
+	if (!cp->orb.cmd.fmt) {
+		pccw1 = to;
+		for (i = 0; i < len; i++) {
+			ccw0 = *(struct ccw0 *)pccw1;
+			if ((pccw1->cmd_code & 0x0f) == CCW_CMD_TIC) {
+				pccw1->cmd_code = CCW_CMD_TIC;
+				pccw1->flags = 0;
+				pccw1->count = 0;
+			} else {
+				pccw1->cmd_code = ccw0.cmd_code;
+				pccw1->flags = ccw0.flags;
+				pccw1->count = ccw0.count;
+			}
+			pccw1->cda = ccw0.cda;
+			pccw1++;
+		}
+	}
+
+	return ret;
 }
 
 /*
@@ -616,9 +643,8 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
 	 * Only support prefetch enable mode now.
 	 * Only support 64bit addressing idal.
 	 * Only support 4k IDAW.
-	 * Only support ccw1.
 	 */
-	if (!orb->cmd.pfch || !orb->cmd.c64 || orb->cmd.i2k || !orb->cmd.fmt)
+	if (!orb->cmd.pfch || !orb->cmd.c64 || orb->cmd.i2k)
 		return -EOPNOTSUPP;
 
 	INIT_LIST_HEAD(&cp->ccwchain_list);