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Re: [qemu-s390x] [RFC 19/19] s390/facilities: enable AP facilities neede
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From: |
Christian Borntraeger |
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Subject: |
Re: [qemu-s390x] [RFC 19/19] s390/facilities: enable AP facilities needed by guest |
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Date: |
Fri, 3 Nov 2017 09:49:46 +0100 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 |
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.