Re: [Qemu-devel] [PATCH v2 0/2] Add machine type pc-1.0-qemu-kvm for live migrate compatibility with qemu-kvm

[Michael S. Tsirkin]

On Fri, Aug 01, 2014 at 08:12:11PM +0100, Alex Bligh wrote:
> This patch series adds inbound migrate capability from qemu-kvm version
> 1.0. The main ideas are those set out in Cole Robinson's patch here:
> http://pkgs.fedoraproject.org/cgit/qemu.git/tree/0001-Fix-migration-from-qemu-kvm.patch?h=f20
> however, rather than patching statically (and breaking inbound
> migration on existing machine types), I have added a new machine
> type (pc-1.0-qemu-kvm) without affecting any other machine types.
> The existing pc-1.0 machine type is renamed to pc-1.0-qemu-git,
> with pc-1.0 becoming an alias for one or another, as selected
> by a configure option (defaulting to pc-1.0-qemu-git, IE no
> change).
> 
> This requires 'hot patching' the VMStateDescription in a couple of
> places, which in turn is less than obvious as there may be (indeed
> are for i8259) derived classes. Whilst pretty nausea-inducing, this
> approach has the benefit of being entirely self-contained.

Ow come on.
Just add a flag and select the appropriate format based on it, using
field_exists.


> I developed this on qemu 2.0 but have forward ported it (trivially)
> to master. My testing has been on a VM live-migrated-to-file from
> Ubuntu Precise qemu-kvm 1.0.
> 
> I have given this a moderate degree of testing but it could do
> with more.
> 
> Note that certain hardware devices (including QXL) will not
> migrate properly due to a fundamental difference in their internal
> state between versions.
> 
> Also note that (as expected) migratino from qemu-2.x to qemu-1.0
> will not work, even if the machine types are the same.
> 
> Alex Bligh (2):
>   Add machine type pc-1.0-qemu-kvm for live migrate compatibility with
>     qemu-kvm
>   Add configure option --enable-pc-1-0-qemu-kvm
> 
>  configure                |   12 ++++++++++++
>  hw/acpi/piix4.c          |   49 
> ++++++++++++++++++++++++++++++++++++++++++++--
>  hw/i386/pc_piix.c        |   39 +++++++++++++++++++++++++++++++++++-
>  hw/timer/i8254_common.c  |   41 ++++++++++++++++++++++++++++++++++++++
>  include/hw/acpi/piix4.h  |    1 +
>  include/hw/timer/i8254.h |    2 ++
>  6 files changed, 141 insertions(+), 3 deletions(-)
> 
> -- 
> 1.7.9.5