[RFC,v2,1/5] vfio-ccw: Fix misleading comment when setting orb.cmd.c64
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Message ID 25a5bf8ae538a392f8483e6fd4b9b165de40bfce.1562616169.git.alifm@linux.ibm.com
State New
Headers show
Series
  • Some vfio-ccw fixes
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Commit Message

Farhan Ali July 8, 2019, 8:10 p.m. UTC
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 what we do in ccwchain_calc_length.

After we have done the ccw processing, it should be safe
to set cmd.c64, since we will convert them into IDALs.

Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
---
 drivers/s390/cio/vfio_ccw_cp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Cornelia Huck July 9, 2019, 9:57 a.m. UTC | #1
On Mon,  8 Jul 2019 16:10:34 -0400
Farhan Ali <alifm@linux.ibm.com> wrote:

> 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 what we do in ccwchain_calc_length.
> 
> After we have done the ccw processing, it should be safe
> to set cmd.c64, since we will convert them into IDALs.

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

>

Fixes: fb9e7880af35 ("vfio: ccw: push down unsupported IDA check")
 
> Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
> ---
>  drivers/s390/cio/vfio_ccw_cp.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
> index d6a8dff..7622b72 100644
> --- a/drivers/s390/cio/vfio_ccw_cp.c
> +++ b/drivers/s390/cio/vfio_ccw_cp.c
> @@ -645,8 +645,8 @@ 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.
> +	/* It is safe to force: if it was not set but idals used
> +	 * ccwchain_calc_length would have returned an error.

Thanks, much clearer.

>  	 */
>  	cp->orb.cmd.c64 = 1;
>  

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

Patch
diff mbox series

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index d6a8dff..7622b72 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -645,8 +645,8 @@  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.
+	/* 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;