DEVICE state was introduced back in 2017:
https://lore.kernel.org/qemu-devel/20171020090556.18631-1-dgilbert@redhat.com/
Quote from Dave's cover letter, when the pre-switchover phase was enabled,
the state transition looks like this:
The precopy flow is:
active->pre-switchover->device->completed
The postcopy flow is:
active->pre-switchover->postcopy-active->completed
To supplement above, when the cap is not enabled:
The precopy flow is:
active->completed
The postcopy flow is:
active->postcopy-active->completed
It works for us, though we have some code just to special case these state
transitions, so the DEVICE state currently is special only to precopy, and
only conditionally.
I had a quick discussion with Libvirt developers, it turns out that this
may not be necessary. IOW, it seems okay we can have DEVICE state to be
generic, so that we don't have over-complicated state machines. It not
only helps align all the migration state machine, help cleanup the code
path especially on pre-switchover handling (see the patch itself), another
side benefit is we can unconditionally have a specific state to mark the
switchover phase, which might be helpful for debugging too.
This patch makes the DEVICE state to be present always, marking that source
QEMU is switching over. Then the state machine will be always as simple
as:
active-> [pre-switchover->] -> device -> [postcopy-active->] -> complete
After the change, no matter whether pre-switchover or postcopy is enabled
or not, we always have DEVICE state showing the switchover phase. When
pre-switchover enabled, we'll have an extra stage before that. When
postcopy is enabled, we'll have an extra stage after that.
A few qtests need touch up in QEMU tree for this change:
- A few iotest outputs (194, 203, 234, 262, 280)
- Teach libqos's migrate() on "device" state
Cc: Jiri Denemark <jdenemar@redhat.com>
Cc: Daniel P. Berrangé <berrange@redhat.com>
Cc: Dr. David Alan Gilbert <dave@treblig.org>
Signed-off-by: Peter Xu <peterx@redhat.com>
Tested-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Juraj Marcin <jmarcin@redhat.com>
Link: https://lore.kernel.org/r/20250114230746.3268797-15-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
This member has been deprecated before the 8.1 release, in commit
34c18203d4 ("qmp: Deprecate 'singlestep' member of StatusInfo").
Time to drop it.
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240117151430.29235-2-philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Launching the destination VM before the source VM gives us a regression
test for HEAD^:
The guest device causes a read from the disk image through
guess_disk_lchs(). This will not work if the first sector (containing
the partition table) is yet unallocated, we use COR, and the node is
inactive.
By launching the source VM before the destination, however, the COR
filter on the source will allocate that area in the image shared between
both VMs, thus the problem will not become apparent.
Switching the launch order causes the sector to still be unallocated
when guess_disk_lchs() runs on the inactive node in the destination VM,
and thus we get our test case.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20191001174827.11081-3-mreitz@redhat.com
Message-Id: <20191001174827.11081-3-mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This test case is motivated by commit 2b23f28639 ('block/copy-on-read:
Fix permissions for inactive node'). Instead of just testing
copy-on-read on migration, let's stack all sorts of filter nodes on top
of each other and try if the resulting VM can still migrate
successfully. For good measure, put everything into an iothread, because
why not?
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
