Re: [Qemu-devel] [PATCH] hw/s390x: Fix the function arguments in the pci stub file

[Thomas Huth <thuth@redhat.com>]

On 2019-02-11 12:04, Cornelia Huck wrote:
> On Mon, 11 Feb 2019 11:54:45 +0100
> Thomas Huth <thuth@redhat.com> wrote:
> 
>> On 2019-02-11 11:48, Cornelia Huck wrote:
>>> On Fri, 1 Feb 2019 09:23:56 +0100
>>> Cornelia Huck <cohuck@redhat.com> wrote:
>>>   
>>>> On Fri, 1 Feb 2019 07:46:40 +0100
>>>> Thomas Huth <thuth@redhat.com> wrote:  
>>>   
>>>>> So I see two options now:
>>>>>
>>>>> 1) Finally really make the device optional, at least for new machine
>>>>> types, so we can really disable CONFIG_PCI and get a working executable.
>>>>>
>>>>> 2) Scratch the idea completely to make this optional, always link the
>>>>> s390-pci-bus.o and s390-pci-inst.o files unconditionally, and remove the
>>>>> s390-pci-stub.c file.
>>>>>
>>>>> I assume options 2 is preferred, since we likely rather want to move
>>>>> into the PCI direction in the long run, instead of ignoring it...    
>>>>
>>>> I think both options are viable, but option 1 is of course more work.
>>>> The win there is that we could disable an entire subsystem.
>>>>
>>>> I guess that the basic questions are: How important is it that
>>>> subsystems can be compiled out, and do we see a use case for a pci-less
>>>> s390 machine in the future? We really don't want to spend much time on
>>>> something of dubious use...  
>>>
>>> Any thoughts on this?
>>>
>>> I'm currently tending towards option 2 (and can cook up a patch for
>>> that). Unless someone is already working on option 1 :)  
>>
>> Since nobody currently has a need to completely disable PCI, I think we
>> should go with option 2.
> 
> Hm... I'm wondering if we also should move S390_FEAT_ZPCI from the max
> cpu model to the qemu cpu model (is there any reason not to turn it on
> by default in tcg?)

Migration compatibility? Wouldn't that cause problems when migrating
back to older versions of QEMU?

 Thomas