Re: [RFC 19/19] s390/facilities: enable AP facilities needed by guest

Martin Schwidefsky
2017-10-16T09:25:10Z

On Fri, 13 Oct 2017 13:39:04 -0400
Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote:

> Sets up the following facilities bits to enable the specified AP
> facilities for the guest VM:
> * STFLE.12: Enables the AP Query Configuration Information
> facility. The AP bus running in the guest uses
> the information returned from this instruction
> to configure AP adapters and domains for the
> guest machine.
> * STFLE.15: Indicates the AP facilities test is available.
> The AP bus running in the guest uses the
> information.
>
> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
> ---
> arch/s390/tools/gen_facilities.c | 2 ++
> 1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/arch/s390/tools/gen_facilities.c b/arch/s390/tools/gen_facilities.c
> index 70dd8f1..eeaa7db 100644
> --- a/arch/s390/tools/gen_facilities.c
> +++ b/arch/s390/tools/gen_facilities.c
> @@ -74,8 +74,10 @@ struct facility_def {
> 8, /* enhanced-DAT 1 */
> 9, /* sense-running-status */
> 10, /* conditional sske */
> + 12, /* AP query configuration */
> 13, /* ipte-range */
> 14, /* nonquiescing key-setting */
> + 15, /* AP special-command facility */
> 73, /* transactional execution */
> 75, /* access-exception-fetch/store indication */
> 76, /* msa extension 3 */

With this all KVM guests will always have the AP instructions available, no?
In principles I like this approach, but it differs from the way z/VM does things,
there the guest will get an exception if it tries to execute an AP instruction
if there are no AP devices assigned to the guest. I wonder if there is a reason
why z/VM does it the way it does.

--
blue skies,
Martin.

"Reality continues to ruin my life." - Calvin.