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Re: [qemu-s390x] [PATCH 02/10] s390x/cpumodel: remove CSSKE from base mo
Re: [qemu-s390x] [PATCH 02/10] s390x/cpumodel: remove CSSKE from base model
Thu, 18 Apr 2019 15:15:50 +0200
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1
On 18.04.19 15:00, Christian Borntraeger wrote:
> On 18.04.19 14:45, David Hildenbrand wrote:
>> On 18.04.19 13:31, Christian Borntraeger wrote:
>>> conditional sske is deprecated and a distant future machine (will be one
>>> where the IBC will not allow to fully go back to z14) will remove this
>>> feature. To prepare for this and allow for the z14 and older cpu model
>>> to still run on systems without csske, remove csske from the base (and
>> will csske feature be a default feature for zNext? Or is it not
>> available *at all*.
>> In case it is not available, baselining and cpu model comparison have to
>> be thought about "ignoring csske".
>>> thus the default models for z10..z14). For compat machines we have to
>>> add those back.
>> Base models are machine-independent. That means, changing base models is
>> not supported.
> Why is that? for the expansion?
Yes, and baselining. It's what the QAPI interface promises.
>> Once we introduce new models like here, we can set the
>> new base models into stone.
> the new model is easy (and yes I could only disable CSSKE in the base
> model for gen15 but not for gen14.
> The problem is that without some kind of fixup for older base models like
> z10-z14 expansion will fall back to z9 on anything that no longer has
I'd prefer to do generate the "right" base models right away and not fix
them up at runtime. They should never change, so fixing them up at
runtime feels wrong.
>> Luckily, we already have "ignored_base_feat", maybe we can simply add
>> csske there and have it working.
> Yes, maybe we could ignore csske.
Yes, that should at least avoid falling back to a z9.
David / dhildenb
[qemu-s390x] [PATCH 06/10] s390x/cpumodel: enhanced sort facility, Christian Borntraeger, 2019/04/18
[qemu-s390x] [PATCH 04/10] s390x/cpumodel: msa9 facility, Christian Borntraeger, 2019/04/18
Re: [qemu-s390x] [Qemu-devel] [PATCH 00/10] s390x: new guest features, no-reply, 2019/04/18
Re: [qemu-s390x] [PATCH 00/10] s390x: new guest features, David Hildenbrand, 2019/04/23
- [qemu-s390x] [PATCH 05/10] s390x/cpumodel: vector enhancements, (continued)