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

Christian Borntraeger
2017-11-03T08:49:46Z

On 11/03/2017 09:14 AM, Harald Freudenberger wrote:
> I talked with the firmware guys about this.
> The answer is that the AP 3 instructions (NQAP, DQAP, PQAP) are always available.

That is true for basic mode and LPAR, but certainly not for z/VM or KVM guests.

> Tony is right with the facility bits.
> facility bit 15 tells if the T bit is supported with the PQAP(TAPQ) subcommand,
> facility bit 12 tells if the PQAP(QCI) subcommand is available.
>
> As far as I could discover the AP instructions where optional on some older machines.
> This may be the reason why zVM throws an exception if there is no AP device assigned.
> However, for all machines still in service the AP instructions are available at al time.

We have to distinguish LPARs and 2nd level guests under KVM/z/VM. For those 2nd level
guests there are configurations out there TODAY that do not support PQAP and friends.