Re: [PATCH v2 03/15] s390: zcrypt: externalize AP instructions available function

[Cornelia Huck]

On Tue, 27 Feb 2018 09:28:01 -0500
Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx> wrote:

> If the AP instructions are not available on the linux host, then
> AP devices can not be interpreted by the SIE. The AP bus has a
> function it uses to determine if the AP instructions are
> available. This patch provides a new function that wraps the
> AP bus's function to externalize it for use by KVM.
> 
> Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx>
> Reviewed-by: Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx>
> ---
>  arch/s390/include/asm/ap.h   |    7 +++++++
>  drivers/s390/crypto/ap_bus.c |    6 ++++++
>  2 files changed, 13 insertions(+), 0 deletions(-)

While I don't see anything wrong with this patch as it stands, you need
to be careful to call this only from vfio-ap code (which depends on
CONFIG_ZCRYPT).

Speaking of which: the ap_bus part cannot be a module, but only
built-in, right? So we don't get additional module complications?