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Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for gua
From: |
Marc Hartmayer |
Subject: |
Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines |
Date: |
Wed, 25 Oct 2017 18:45:51 +0200 |
On Wed, Oct 25, 2017 at 05:50 PM +0200, David Hildenbrand <address@hidden>
wrote:
> On 25.10.2017 17:09, Boris Fiuczynski wrote:
>> On 10/25/2017 12:23 PM, David Hildenbrand wrote:
>>> On 25.10.2017 12:18, Christian Borntraeger wrote:
>>>> Ping, I plan to submit belows patch for 2.11. We can then still look into
>>>> a libvirt<->qemu interface for limiting host-model depending on machine
>>>> versions
>>>> (or not).
>>>
>>> I think this would be sufficient for now.
>>>
>>> Having different host models, depending on the the machine type sounds
>>> wrong. But maybe we'll need it in the future.
>>>
>>
>> David, I disagree if your proposal is to generally tolerate new cpu
>> features in old machine types. This *might* work for gs but how do you
>> guaranty that guests do not behave differently/wrong when suddenly new
>> cpu features are made available to guest when (re-)starting them.
>> That is my feedback for the qemu side of this mater.
>
> Just re-reading this section, so what you mean is:
>
> a) guest is started, host model is copied and used. guest works.
> b) guest is stopped.
> c) QEMU/KVM/HW is updated.
> d) guest is started, new host model is copied. guest no longer works.
>
> d) could be because there are now some additional features with e.g.
> broken guest implementation or now missing features.
>
>
> What you propose (if I am not wrong) is a to bind features somehow to a
> QEMU machine. I think that should never be done. You could not catch now
> missing features.
What exactly do you mean by the last sentence?
>
> What would you think about a persistent host-model copy option? So
> instead of copying at every start, only copy and replace it once in the XML?
>
> Easy to specify by the user and no CPU feature changes will happend
> "blindly".
>
>
> --
>
> Thanks,
>
> David
>
--
Beste Grüße / Kind regards
Marc Hartmayer
IBM Deutschland Research & Development GmbH
Vorsitzende des Aufsichtsrats: Martina Koederitz
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen
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- [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, Christian Borntraeger, 2017/10/20
- Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, Christian Borntraeger, 2017/10/20
- Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, Christian Borntraeger, 2017/10/25
- Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, David Hildenbrand, 2017/10/25
- Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, Boris Fiuczynski, 2017/10/25
- Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, David Hildenbrand, 2017/10/25
- Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, David Hildenbrand, 2017/10/25
- Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines,
Marc Hartmayer <=
- Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, David Hildenbrand, 2017/10/26
- Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, Jiri Denemark, 2017/10/27
Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, Jason J. Herne, 2017/10/25
Re: [Qemu-devel] [libvirt] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, Christian Borntraeger, 2017/10/27
Re: [Qemu-devel] [libvirt] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, Christian Borntraeger, 2017/10/27
Re: [Qemu-devel] [libvirt] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, Halil Pasic, 2017/10/27