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