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

[Eduardo Habkost]

On Wed, Jul 05, 2017 at 12:32:10PM +0300, Marcel Apfelbaum wrote:
> On 05/07/2017 11:14, Thomas Huth wrote:
> >   Hi,
> > 
> 
> 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.
> > 
> 
> Agreed
> 
> > Yes, IMHO at one point in time, we should switch the default machine
> > type to q35.
> 
> +1
> 
> > 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 ...
> 
> I am not so sure about that. Developers working on upstream projects
> should expect such changes and, for our case,
> modifying the command line by adding "-M pc" should not be a big deal.

We could print a warning for 1 or 2 releases when users don't add
a explicit "-M pc" or "-M q35" argument to qemu-system-x86_64,
but:

> 
> The upper layers should manage the defaults by themselves so
> are not supposed to be affected.

But they would be.  libvirt uses the default machine-type from
QEMU.


> [...]

-- 
Eduardo