Re: [Qemu-devel] [PATCH/RFC 2/3] s390x/ais: enable ais when migration is available

[Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>]

On 09/26/2017 11:14 AM, Yi Min Zhao wrote:
> 
> 
> 在 2017/9/25 下午7:47, Christian Borntraeger 写道:
>> On 09/25/2017 01:45 PM, Cornelia Huck wrote:
>>> On Mon, 25 Sep 2017 12:12:49 +0200
>>> Christian Borntraeger <borntraeger@de.ibm.com> wrote:
>>>
>>>> On 09/25/2017 12:07 PM, Cornelia Huck wrote:
>>>>> On Fri, 22 Sep 2017 16:27:00 +0200
>>>>> Halil Pasic <pasic@linux.vnet.ibm.com> wrote:
>>>>>> One thing I would find very helpful is what do we expect to work 
>>>>>> and not
>>>>>> work for which version. Kind of a matrix. For instance should vfio 
>>>>>> pci
>>>>>> work for versions prior 2.11. I think in the not so distant past we
>>>>>> changed how SIC works (so it complains when we don't have ais).
>>>>> A matrix sounds like a good idea.
>>>> I think we do not even need a matrix, a minimum level will suffice 
>>>> because...
>>>>> I don't think we really ever had a setup that worked out of the box
>>>> exactly: ...it never worked until 2.10 and we do not have libvirt 
>>>> support yet.
>>>> Now with the fix 2.10 will also not work, so I think its fair to say
>>>>
>>>> PCI passthrough via VFIO will be supported for
>>>> - KVM: host kernel >= 4.13
>>>> - TCG: TBD
>>>> - QEMU >= 2.11
>>>> - libvirt TBD
>>> Make that zpci-per-se, no?
>>>
>>> with KVM: host kernel >= 4.13 && QEMU >= 2.11
>>> with TCG: tbd, I don't think anybody has time to wire this up for 2.11
>>>
>>> Apropos libvirt: How will it determine whether zpci should be
>>> supported? There are some old QEMU + KVM combinations out there that
>>> will have a phb (but not be usable by stock Linux guests as the feature
>>> bits are missing). Version fence? Check for cpu feature support?
>> I think for multibus or something like that Boris wanted to check for 
>> a version
>> anyway. So maybe 2.11 (now that 2.10 is broken regarding ais) as a 
>> minimum QEMU
>> level would make sense.
>>
>>
> I think this makes sense. But I think I have to discuss this with Boris.
In libvirt multibus is one of the few (very old) supports that would 
allow checking against a qemu version.
Detection of zpci support is another matter since that capability is 
tied to the existence of the zpci object in qom. Tying the zpci 
capability to the multibus support has its pro and cons. I have not made 
up my mind yet.


-- 
Mit freundlichen Grüßen/Kind regards
    Boris Fiuczynski

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