Re: [libvirt] [Qemu-devel] [PATCH] [RFC] Add machine type pc-1.0-qemu-kvm for live migrate compatibility with qemu-kvm
On Mon, Aug 04, 2014 at 04:47:11PM +0100, Alex Bligh wrote:
On 4 Aug 2014, at 16:38, Serge Hallyn <serge.hallyn(a)ubuntu.com> wrote:
>>
>> If you really want it to be called pc-1.0, you
>> can make it a machine property instead.
>> E.g. qemu-kvm-compatibility.
>> Teach management to set it if remote is qemu-kvm:
>> -machine pc-1.0,qemu-kvm-compatibility=on
>
> That sounds nice - Alex, what do you think?
Not having used the machine property stuff before,
or played with libvirt much, I'm not sure how this
helps libvirt.
I thought the issue here was that migrating from
1.0-qemu-kvm to 2.x OR 1.0-qemu-git to 2.x, libvirt
is going to to supply the same command line.
As
libvirt doesn't know what the sender is (and
it's not possible to detect this automatically -
at least not without a far more intrusive patch),
Yes, this is up to higher level user.
At libvirt xml level, you would just specify
something like "legacy qemu-kvm compatibility" in the xml.
one has to make a choice at build time as to what
'pc-1.0' represents.
There's no choice really. Downstreams must make sure
their machine types are distinct from upstream ones.
qemu-kvm as a downstream violated this rule but
I don't think this means upstream should violate it.
This is what patch #2 does.
I fully agree it is not pretty.
The problem is not prettyness.
The problem is, it creates a situation where two instances
of qemu have different ideas about what a specific
machine type is.
So I am not sure why
-machine pc-1.0,qemu-kvm-compatibility=on
is any easier for libvirt than
-machine pc-1.0-qemu-kvm
IE what does using a machine property rather than
a machine type buy us?
Seems to be easier to understand that it maps to pc-1.0
on the other side.
--
Alex Bligh