Re: [libvirt] [Qemu-devel] [PATCH v4] Add machine parameter qemu-kvm-migration for live migrate compatibility with qemu-kvm
Michael,
I'm about to post a nice simple v5 of this, but there are a couple of
your comments I am NOT addressing:
>
> diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
> index b72b34e..3c9da23 100644
> --- a/hw/acpi/piix4.c
> +++ b/hw/acpi/piix4.c
> @@ -200,12 +200,26 @@ static const VMStateDescription vmstate_pci_status = {
> }
> };
>
> +static const VMStateDescription vmstate_acpi_compat;
> +
don't forward declare things, put them right here.
This is not addressable in v5; in v5 this is a forward declaration of
vmstate_acpi (not _compat). vmstate_acpi references acpi_load_old,
and acpi_load_old references vmstate_acpi, so we need a forward
reference for one of them in any case.
> + qemu_opt_get_bool(qemu_get_machine_opts(),
"qemu-kvm-migration",
> + DEFAULT_QEMU_KVM_MIGRATION)) {
> + return vmstate_load_state(f, &vmstate_acpi_compat,
> + opaque, version_id);
> + }
else if version_id == 2 return -EINVAL?
This is incorrect I think. A version_id of 2 with qemu-kvm_migration
off is permissible, and indicates an inbound migration from qemu-git
1.2, i.e. the old manual loading should be run.
> /* qemu-kvm 1.2 uses version 3 but advertised as 2
> - * To support incoming qemu-kvm 1.2 migration, change version_id
> - * and minimum_version_id to 2 below (which breaks migration from
> + * To support incoming qemu-kvm 1.2 migration, we support
> + * via a command line option a change to minimum_version_id
> + * of 2 in a _compat structure (which breaks migration from
> * qemu 1.2).
Actually it's version 3 that breaks migration right?
Pls say this explicitly: s/which/version 3 breaks migration from qemu 1.2/
It's changing the minimum version ID to 2 (from 3) which would break
migration from qemu (git) 1.2, because that uses a version ID of 2,
and we want the old loader to run in that case. I've made this clearer.
--
Alex Bligh