From: Peter Xu <peterx@redhat.com>
To: Avihai Horon <avihaih@nvidia.com>
Cc: qemu-devel@nongnu.org, "Alex Williamson" <alex@shazbot.org>,
"Cédric Le Goater" <clg@redhat.com>,
"Fabiano Rosas" <farosas@suse.de>,
"Pierrick Bouvier" <pierrick.bouvier@oss.qualcomm.com>,
"Philippe Mathieu-Daudé" <philmd@mailo.com>,
"Zhao Liu" <zhao1.liu@intel.com>,
"Halil Pasic" <pasic@linux.ibm.com>,
"Christian Borntraeger" <borntraeger@linux.ibm.com>,
"Jason Herne" <jjherne@linux.ibm.com>,
"Richard Henderson" <richard.henderson@linaro.org>,
"Ilya Leoshkevich" <iii@linux.ibm.com>,
"David Hildenbrand" <david@kernel.org>,
"Eric Farman" <farman@linux.ibm.com>,
"Matthew Rosato" <mjrosato@linux.ibm.com>,
"Cornelia Huck" <cohuck@redhat.com>,
"Eric Blake" <eblake@redhat.com>,
"Vladimir Sementsov-Ogievskiy" <vsementsov@yandex-team.ru>,
"John Snow" <jsnow@redhat.com>,
"Markus Armbruster" <armbru@redhat.com>,
"Maor Gottlieb" <maorg@nvidia.com>
Subject: Re: [PATCH v3 08/14] migration: Fail migration if switchover-ack is requested after switchover decision
Date: Fri, 12 Jun 2026 12:17:45 -0400 [thread overview]
Message-ID: <aiwxKUF9uKAgYuK7@x1.local> (raw)
In-Reply-To: <20260609075812.32067-9-avihaih@nvidia.com>
On Tue, Jun 09, 2026 at 10:58:06AM +0300, Avihai Horon wrote:
> Switchover ACK is checked only during precopy while the guest is still
> running. The last migration_can_switchover() decision and guest stop are
> not atomic, so a device may want to request another switchover ACK in
> the gap after switchover decision has been made but before the guest is
> stopped. Migration would then miss that request, which can increase
> downtime.
>
> Cover this case by failing the migration if a switchover-ack was
> requested during that time.
>
> Ideally, precopy iterations should be resumed in this case, however,
> VFIO doesn't support going back to precopy after being stopped, so
> implementing such logic would require non-trivial changes to the guest
> start/stop flow. Given the above and that this case should be rare,
> failing the migration seems reasonable.
>
> Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
--
Peter Xu
next prev parent reply other threads:[~2026-06-12 16:18 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-09 7:57 [PATCH v3 00/14] Make switchover-ack re-usable and add VFIO precopy REINIT feature Avihai Horon
2026-06-09 7:57 ` [PATCH v3 01/14] migration: Propagate errors in migration_completion_precopy() Avihai Horon
2026-06-09 12:11 ` Philippe Mathieu-Daudé
2026-06-12 16:03 ` Peter Xu
2026-06-14 9:34 ` Avihai Horon
2026-06-09 7:58 ` [PATCH v3 02/14] migration/ram: Use migration_bitmap_sync_precopy() for postcopy discard Avihai Horon
2026-06-12 15:59 ` Peter Xu
2026-06-09 7:58 ` [PATCH v3 03/14] migration: Run final save_query_pending at switchover Avihai Horon
2026-06-12 16:03 ` Peter Xu
2026-06-09 7:58 ` [PATCH v3 04/14] migration: Log the approver in qemu_loadvm_approve_switchover() Avihai Horon
2026-06-09 7:58 ` [PATCH v3 05/14] migration: Replace switchover_ack_needed SaveVMHandler Avihai Horon
2026-06-09 7:58 ` [PATCH v3 06/14] migration: Rename switchover-ack code to legacy Avihai Horon
2026-06-09 7:58 ` [PATCH v3 07/14] migration: Make switchover-ack re-usable Avihai Horon
2026-06-12 16:16 ` Peter Xu
2026-06-14 9:50 ` Avihai Horon
2026-06-15 13:34 ` Peter Xu
2026-06-15 14:35 ` Avihai Horon
2026-06-09 7:58 ` [PATCH v3 08/14] migration: Fail migration if switchover-ack is requested after switchover decision Avihai Horon
2026-06-12 16:17 ` Peter Xu [this message]
2026-06-09 7:58 ` [PATCH v3 09/14] vfio/migration: Extract VFIO_MIG_FLAG_DEV_INIT_DATA_SENT sending to helper Avihai Horon
2026-06-09 7:58 ` [PATCH v3 10/14] vfio/migration: Add Error ** parameter to vfio_migration_init() Avihai Horon
2026-06-09 12:09 ` Cédric Le Goater
2026-06-09 7:58 ` [PATCH v3 11/14] vfio/migration: Add new switchover-ack mechanism Avihai Horon
2026-06-09 7:58 ` [PATCH v3 12/14] vfio/migration: Implement VFIO_PRECOPY_INFO_REINIT feature Avihai Horon
2026-06-09 7:58 ` [PATCH v3 13/14] vfio/migration: Check VFIO_PRECOPY_INFO_REINIT during switchover Avihai Horon
2026-06-12 16:22 ` Peter Xu
2026-06-09 7:58 ` [PATCH v3 14/14] migration: Enable new switchover-ack Avihai Horon
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