[libvirt PATCH 06/80] qemu: Keep domain running on dst on failed post-copy migration

[Peter Krempa]

On Tue, May 10, 2022 at 17:20:27 +0200, Jiri Denemark wrote:
> There's no need to artificially pause a domain when post-copy fails. The
> virtual CPUs may continue running, only the guest tasks that decide to
> read a page which has not been migrated yet will get blocked.

IMO not pausing the VM is a policy decision (same way as pausing it was
though) and should be user-configurable at migration start.

I can see that users might want to prevent a half-broken VM from
executing until it gets attention needed to fix it, even when it's safe
from a "theoretical" standpoint.

> 
> Signed-off-by: Jiri Denemark <jdenemar at redhat.com>
> ---
>  src/qemu/qemu_migration.c | 37 +++++++++++++++++++++++++++++++++----
>  src/qemu/qemu_migration.h |  6 ++++--
>  src/qemu/qemu_process.c   |  8 ++++----
>  3 files changed, 41 insertions(+), 10 deletions(-)

The code looks okay, but I think this needs more justification if it's
to be accepted in this state.