[fedora-virt] [fedora-specific libvirt PATCH] qemu: replace deprecated fedora-13 machine type with pc-0.13

[Amit Shah]

On (Tue) 13 Dec 2011 [06:09:01], Eric Blake wrote:
> On 12/12/2011 11:35 PM, Amit Shah wrote:
> > On (Mon) 12 Dec 2011 [17:00:57], Eric Blake wrote:
> >> Testing results - upgrading libvirtd with a running domain of type
> >> fedora-13 passed, and I noticed all persistent configurations were
> >> properly upgraded as part of the new libvirtd.  All attempts to modify a
> >> running fedora-13 machine were converted to pc-0.13, as expected by the
> >> code.
> >>
> >> HOWEVER, pc-0.13 is wrong.  I had one rather significant test failure:
> >>
> >>
> >> succeeded.  My conclusion?  Qemu must be saving the machine type
> >> somewhere in the migration file format (virsh save is a migration to
> >> file, which means you'd see the same behavior when migrating between two
> >> machines); and pc-0.13 is missing something related to kvmclock, and is
> >> thus unable to reparse the migration data.  But pc-0.14 works just fine,
> >> which means your patch is _almost_ right - just change fedora-13 to
> >> pc-0.14, and I think we're set.
> > 
> > The fedora-13 machine type was just a slightly modified pc-0.12
> > machine type, so using pc-0.12 should be the safest.
> 
> That's wrong.  The whole reason fedora-13 was introduced was because it
> exposed MORE features than stock pc-0.12, so it is closer either to
> pc-0.13 or to pc-0.14.

I wonder how you say that.  It's closer to pc-0.12 since there was
exactly one feature additional in fedora-13 since pc-0.12.  The
features added in pc-0.13 and pc-0.14 are not assessed for their
impact in all the cases.  The fact that we saw kvmclock-related
changes break things should be a red flag.  For the test that failed,
loading from a saved image, did you try using pc-0.12 and see if that
breaks anything?  If it doesn't, won't you say it's better to use
pc-0.12?

>  I already proved that we can't do migration from
> fedora-13 to pc-0.13, but can do migration to pc-0.14, which means that,
> at least in F16, fedora-13 is a synonym to pc-0.14, not pc-0.12.

These really are things that we can't exhaustively test.  Eg., do
Windows guests complain of device changes?  Do they need
re-activation?

		Amit