[Qemu-devel] [PATCH v3 0/2] Add machine type pc-1.0-qemu-kvm for live migrate compatibility with qemu-kvm

[Alex Bligh <alex@alex.org.uk>]

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).

Two aproaches are taken:

* In hw/timer/i8254_common.c, the VMSTATE_UINT32_TEST macro
  is used to test the version for the irq_disable flags,
  allowing version 3 or more, or version 2 for an inbound
  migrate from qemu-kvm (only).

* In hw/acpi/piix4.c, qemu-kvm incorrectly uses version 2 for
  a version 3 structure, causing acpi_load_old to be used.
  acpi_load_old detects this situation based on the machine type
  and restarts the attempt to load the vmstate using a
  customised VMStateDescription. The above cleaner approach is
  unavailable here.

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) migration 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         |   47 +++++++++++++++++++++++++++++++++++++++++++++--
 hw/i386/pc_piix.c       |   38 +++++++++++++++++++++++++++++++++++++-
 hw/timer/i8254_common.c |   10 +++++++++-
 4 files changed, 103 insertions(+), 4 deletions(-)

-- 
1.7.9.5