linux-kernel - [PATCH v2 1/1] s390: vfio-ccw: push down unsupported IDA check

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Date:   Wed, 16 May 2018 19:33:42 +0200
From:   Halil Pasic <pasic@...ux.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>,
        Dong Jia Shi <bjsdjshi@...ux.ibm.com>
Cc:     Halil Pasic <pasic@...ux.ibm.com>,
        "Jason J. Herne" <jjherne@...ux.ibm.com>,
        linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/1] s390: vfio-ccw: push down unsupported IDA check

There is at least one relevant guest OS that doesn't set the IDA flags in
the ORB as we would like them, but never uses any IDA. So instead of
saying -EOPNOTSUPP when observing an ORB, such that a channel program
specified by it could be a not supported one, let us say -EOPNOTSUPP only
if the channel program is a not supported one.

Of course, the real solution would be doing proper translation for all
IDA. This is possible, but given the current code not straight forward.

Signed-off-by: Halil Pasic <pasic@...ux.ibm.com>
Tested-by: Jason J. Herne <jjherne@...ux.ibm.com>
---
---
 drivers/s390/cio/vfio_ccw_cp.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index 2c7550797ec2..cb4bf0dfbacc 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -365,6 +365,9 @@ static void cp_unpin_free(struct channel_program *cp)
  * This is the chain length not considering any TICs.
  * You need to do a new round for each TIC target.
  *
+ * The program is also validated for absence of not yet supported
+ * indirect data addressing scenarios.
+ *
  * Returns: the length of the ccw chain or -errno.
  */
 static int ccwchain_calc_length(u64 iova, struct channel_program *cp)
@@ -391,6 +394,14 @@ static int ccwchain_calc_length(u64 iova, struct channel_program *cp)
 	do {
 		cnt++;
 
+		/*
+		 * As we don't want to fail direct addressing even if the
+		 * orb specified one of the unsupported formats, we defer
+		 * checking for IDAWs in unsupported formats to here.
+		 */
+		if ((!cp->orb.cmd.c64 || cp->orb.cmd.i2k) && ccw_is_idal(ccw))
+			return -EOPNOTSUPP;
+
 		if ((!ccw_is_chain(ccw)) && (!ccw_is_tic(ccw)))
 			break;
 
@@ -656,10 +667,8 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
 	/*
 	 * XXX:
 	 * Only support prefetch enable mode now.
-	 * Only support 64bit addressing idal.
-	 * Only support 4k IDAW.
 	 */
-	if (!orb->cmd.pfch || !orb->cmd.c64 || orb->cmd.i2k)
+	if (!orb->cmd.pfch)
 		return -EOPNOTSUPP;
 
 	INIT_LIST_HEAD(&cp->ccwchain_list);
@@ -688,6 +697,10 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
 	ret = ccwchain_loop_tic(chain, cp);
 	if (ret)
 		cp_unpin_free(cp);
+	/* It is safe to force: if not set but idals used
+	 * ccwchain_calc_length returns an error.
+	 */
+	cp->orb.cmd.c64 = 1;
 
 	return ret;
 }
-- 
2.16.3