[libvirt] [PATCH] qemu: Fix domain resume after failed migration

[Ján Tomko]

On Mon, Jun 04, 2018 at 04:51:18PM +0200, Jiri Denemark wrote:
>Libvirt relies on being able to kill the destination domain and resume
>the source one during migration until we called "cont" on the
>destination. Unfortunately, QEMU automatically activates block devices
>at the end of migration even when it's called with -S. This wasn't a big
>issue in the past since the guest is not running and thus no data are
>written to the block devices. However, when QEMU introduced its internal
>block device locks, we can no longer resume the source domain once the
>destination domain already activated the block devices (and thus
>acquired all locks) unless the destination domain is killed first.
>
>Since it's impossible to synchronize the destination and the source
>libvirt daemons after a failed migration, QEMU introduced a new
>migration capability called "late-block-activat" which ensures QEMU

activate

>won't activate block devices until it gets "cont". The only thing we
>need to do is to enable this capability whenever QEMU supports it.
>
>https://bugzilla.redhat.com/show_bug.cgi?id=1568407
>
>QEMU commit implementing the capability: v2.12.0-952-g0f073f44df
>
>Signed-off-by: Jiri Denemark <jdenemar at redhat.com>
>---
> src/qemu/qemu_migration_params.c | 4 ++++
> src/qemu/qemu_migration_params.h | 1 +
> 2 files changed, 5 insertions(+)
>

Only five insertions? You could have at least added a test :P

Reviewed-by: Ján Tomko <jtomko at redhat.com>

Jano
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