Markus, On 24 Sep 2014, at 09:05, Markus Armbruster <armbru@redhat.com> wrote:
Alex Bligh <alex@alex.org.uk> writes:
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-qem... however, rather than patching statically (and breaking inbound migration on existing machine types), I have added a new machine parameter (qemu-kvm-migration) which when turned on affects the pc-1.0 machine type. Usage: -machine pc-1.0,qemu-kvm-migration=on
Forgive me if this has been discussed already: why not simply a separate machine type "pc-1.0-qemu-kvm"?
That's what v2 of the patch set does (and I prefer v2). However, mst wanted it done this way.
Three aproaches are taken:
* cirrus-vga.vgamem_mb defaults to 16 rather than 8. In order to keep -global cirrus-vga.vgamem_mb working even with qemu-kvm-migration=on, this is monkey-patched into the default value of the MachineState structure's compat_props list.
This part fires only for pc-1.0, because it's in pc_early_init_pci_1_0().
Yes, intentional. I should have noted that. That's because qemu-kvm-migration=on the VRAM change was designed to work only with pc-1.0. I haven't looked at trying to make other (older) qemu-kvm machine migrations work, but (with the stuff below), I would guess it would work with the appropriate command line options for VRAM size. Obviously I could put early init elsewhere.
* 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.
These parts apply to all machine types, don't they?
They apply only when qemu-kvm-migration=on is selected, but to any machine type; however machine types newer than pc-1.0 will be exporting v3 I think anyway.
Changes since v1: * Do not use a machine type, use a machine parameter.
Okay, it has been discussed already. I'd appreciate a brief recap all the same.
See above. I preferred the machine type. But I got to learn more about QOM on the way :-) -- Alex Bligh