Re: [Qemu-devel] change x86 default machine type to Q35?

[Thomas Huth]

On 05.07.2017 13:07, Daniel P. Berrange wrote:
> On Wed, Jul 05, 2017 at 10:14:23AM +0200, Thomas Huth wrote:
>>  Hi,
>>
>> On 05.07.2017 08:57, Chao Peng wrote:
>>>
>>> Q35 has been in QEMU for quite a while. Compared to the current default
>>> i440FX, Q35 is probably not that mature and not widely used, however in
>>> some case, Q35 has advantages, for example, in supporting new features.
>>> For instance, we have some features require PCI-e support which is only
>>> available on Q35 and some others need it for EFI support. It is of
>>> course not necessary to change it as the default but if more and more
>>> features have dependencies on Q35 because of requiring much more modern
>>> features then I think it may be worth to do so. In such case we can have
>>> more people to use it and find problems we may know or not know.
>>
>> Yes, IMHO at one point in time, we should switch the default machine
>> type to q35. The i440FX is really quite old...
>>
>>> There are certainly some drawbacks:
>>> -        Compatibility: current code or script may need adjustment
>>
>> That might be a real concern ... so I think a good point in time to
>> switch to the q35 machine type would be when we switch to the next major
>> version number of QEMU, i.e. when we switch to version 3.0. If the users
>> see a new major version number, they might be more willing to accept
>> such major changes (yeah, I know, we've discussed in the past that
>> version numbers are just numbers ... but still, there is some kind of
>> psychological aspect to this, too, I think)
> 
> Most users aren't even aware of version numbers of QEMU - they'll just
> take whatever their distro has provided run it. The notion that their
> latest distro version happened to pull in a "major" version instead of
> previously pulling in a "minor" version is invisible to everyone,
> except the minority of people who care about the low level details.

Well, but those users who do not care at all hopefully use libvirt,
GNOME boxes or a similar management layer to start their virtual
machines, so it should not matter for them at all.

 Thomas