[PATCH v3 1/5] vfio-ccw: Fix misleading comment when setting orb.cmd.c64

From: Farhan Ali <alifm@linux.ibm.com>
To: cohuck@redhat.com, farman@linux.ibm.com, pasic@linux.ibm.com
Cc: linux-s390@vger.kernel.org, kvm@vger.kernel.org, alifm@linux.ibm.com
Subject: [PATCH v3 1/5] vfio-ccw: Fix misleading comment when setting orb.cmd.c64
Date: Thu, 11 Jul 2019 10:28:51 -0400	[thread overview]
Message-ID: <f68636106aef0faeb6ce9712584d102d1b315ff8.1562854091.git.alifm@linux.ibm.com> (raw)
In-Reply-To: <cover.1562854091.git.alifm@linux.ibm.com>
In-Reply-To: <cover.1562854091.git.alifm@linux.ibm.com>

The comment is misleading because it tells us that
we should set orb.cmd.c64 before calling ccwchain_calc_length,
otherwise the function ccwchain_calc_length would return an
error. This is not completely accurate.

We want to allow an orb without cmd.c64, and this is fine
as long as the channel program does not use IDALs. But we do
want to reject any channel program that uses IDALs and does
not set the flag, which is what we do in ccwchain_calc_length.

After we have done the ccw processing, we need to set cmd.c64,
as we use IDALs for all translated channel programs.

Also for better code readability let's move the setting of
cmd.c64 within the non error path.

Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
---
 drivers/s390/cio/vfio_ccw_cp.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index d6a8dff..c969d48 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -645,14 +645,15 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
 	if (ret)
 		cp_free(cp);
 
-	/* It is safe to force: if not set but idals used
-	 * ccwchain_calc_length returns an error.
-	 */
-	cp->orb.cmd.c64 = 1;
-
-	if (!ret)
+	if (!ret) {
 		cp->initialized = true;
 
+		/* It is safe to force: if it was not set but idals used
+		 * ccwchain_calc_length would have returned an error.
+		 */
+		cp->orb.cmd.c64 = 1;
+	}
+
 	return ret;
 }
 
-- 
2.7.4
