Re: [PATCH v2 7/7] s390/cio: Remove vfio-ccw checks of command codes

Cornelia Huck
2019-05-15T12:43:09Z

On Wed, 15 May 2019 01:42:48 +0200
Eric Farman <farman@linux.ibm.com> wrote:

> If the CCW being processed is a No-Operation, then by definition no
> data is being transferred. Let's fold those checks into the normal
> CCW processors, rather than skipping out early.
>
> Likewise, if the CCW being processed is a "test" (an invented
> definition to simply mean it ends in a zero), let's permit that to go
> through to the hardware. There's nothing inherently unique about
> those command codes versus one that ends in an eight [1], or any other
> otherwise valid command codes that are undefined for the device type
> in question.

Hm... let's tweak that a bit? It's not that "test" is an invented
category; it's just that this has not been a valid command for
post-s/370 and therefore should not get any special treatment and just
be sent to the hardware?

>
> [1] POPS states that a x08 is a TIC CCW, and that having any high-order
> bits enabled is invalid for format-1 CCWs. For format-0 CCWs, the
> high-order bits are ignored.
>
> Signed-off-by: Eric Farman <farman@linux.ibm.com>
> ---
> drivers/s390/cio/vfio_ccw_cp.c | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)