Re: [Xen-devel] [PATCH] Remove hardcoded xen-platform device initialization

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Stefano Stabellini [mailto:stefano.stabellini@xxxxxxxxxxxxx]
> Sent: 18 June 2013 20:35
> To: Paolo Bonzini
> Cc: Stefano Stabellini; Paul Durrant; qemu-devel@xxxxxxxxxx; xen-
> devel@xxxxxxxxxxxxx; Ian Campbell
> Subject: Re: [Xen-devel] [PATCH] Remove hardcoded xen-platform device
> initialization
> 
> On Tue, 18 Jun 2013, Paolo Bonzini wrote:
> > Il 18/06/2013 20:56, Stefano Stabellini ha scritto:
> > >> >
> > >> > Ok. I guess we can have the ability to override the machine type in the
> VM config, so you could still kick off an older qemu with a newer libxl - but 
> it
> sounds like the auto-discovery idea is a no-go then.
> > > xenfv-2.0 is a bad idea, like Paolo wrote, it should be possible to just
> > > use -M pc for HVM guests and retain -M xenpv for pv guests.
> > >
> > > However it seems to me that we also need a way in libxl to find out
> > > whether QEMU is new enough for us to be able to use -M pc.
> > > We can't just assume that users will be able to figure out the magic
> > > rune they need to write in the VM config file to solve their VM crash at
> > > boot problem.
> > >
> > > We could spawn an instance of QEMU just to figure out the QEMU
> version
> > > but we certainly cannot do that every time we start a new VM.
> > > Once we figure out the QEMU version the first time we could write it to
> > > xenstore so that the next time we don't have to go through the same
> > > process again.
> >
> > Can you just assume that 4.4 requires QEMU 1.6 or newer?
> 
> I would rather not make that assumption because we cannot control what
> distro are going to package. I wouldn't want a distro to ship with Xen
> HVM guests broken because they choose the wrong QEMU version. Of
> course
> we could put that in the release notes, but there are lots of distros
> out there and I am pretty sure that at least one of them is not going to
> read them.

Can't we just leave the default set at xenfv (as it is in my patch) until we're 
happy that most distros are carrying a new enough qemu?

  Paul

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