The expected outcome from qmp_migrate_cancel() is that the source
migration goes to the terminal state
MIGRATION_STATUS_CANCELLED. Anything different from this is a bug when
cancelling.
Make sure there is never a state transition from an unspecified state
into FAILED. Code that sets FAILED, should always either make sure
that the old state is not CANCELLING or specify the old state.
Note that the destination is allowed to go into FAILED, so there's no
issue there.
(I don't think this is relevant as a backport because cancelling does
work, it just doesn't show the right state at the end)
Fixes: 3dde8fdbad ("migration: Merge precopy/postcopy on switchover start")
Fixes: d0edb8a173 ("migration: Create the postcopy preempt channel asynchronously")
Fixes: 8518278a6a ("migration: implementation of background snapshot thread")
Fixes: bf78a046b9 ("migration: refactor migrate_fd_connect failures")
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-ID: <20250213175927.19642-7-farosas@suse.de>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
After postcopy has started, it's not possible to recover the source
machine in case a migration error occurs because the destination has
already been changing the state of the machine. For that same reason,
it doesn't make sense to try to cancel the migration after postcopy
has started. Reject the cancel command during postcopy.
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-ID: <20250213175927.19642-6-farosas@suse.de>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Remove all instances of _fd_ from the migration generic code. These
functions have grown over time and the _fd_ part is now just
confusing.
migration_fd_error() -> migration_error() makes it a little
vague. Since it's only used for migration_connect() failures, change
it to migration_connect_set_error().
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-ID: <20250213175927.19642-4-farosas@suse.de>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
There's no need for two separate functions and this _fd_ is a historic
artifact that makes little sense nowadays.
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-ID: <20250213175927.19642-3-farosas@suse.de>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
There's no point passing the error into migration cancel only for it
to call migrate_set_error().
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-ID: <20250213175927.19642-2-farosas@suse.de>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
The general expectation is that header files should follow the same
file/path naming scheme as the corresponding source file. There are
various historical exceptions to this practice in QEMU, with one of
the most notable being the include/qapi/qmp/ directory. Most of the
headers there correspond to source files in qobject/.
This patch corrects most of that inconsistency by creating
include/qobject/ and moving the headers for qobject/ there.
This also fixes MAINTAINERS for include/qapi/qmp/dispatch.h:
scripts/get_maintainer.pl now reports "QAPI" instead of "No
maintainers found".
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Acked-by: Halil Pasic <pasic@linux.ibm.com> #s390x
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20241118151235.2665921-2-armbru@redhat.com>
[Rebased]
Block devices have an individual active state, a single global flag
can't cover this correctly. This becomes more important as we allow
users to manually manage which nodes are active or inactive.
Now that it's allowed to call bdrv_inactivate_all() even when some
nodes are already inactive, we can remove the flag and just
unconditionally call bdrv_inactivate_all() and, more importantly,
bdrv_activate_all() before we make use of the nodes.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20250204211407.381505-5-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Now after all the cleanups, finally we can merge the switchover startup
phase into one single function for precopy/postcopy.
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/20250114230746.3268797-16-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
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>
Postcopy invokes qemu_savevm_state_complete_precopy() twice for a long
time, and that caused way too much confusions. Let's clean this up and
make postcopy easier to read.
It's actually fairly straightforward: postcopy starts with saving
non-postcopiable iterables, then later it saves again with non-iterable
only. Move these two calls out makes everything much easier to follow.
Otherwise it's very unclear what qemu_savevm_state_complete_precopy() did
in either of the calls.
No functional change intended.
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/20250114230746.3268797-13-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Postcopy invokes qemu_savevm_state_complete_precopy() twice, that means
it'll invoke COMPLETE notify twice.. also twice the tracepoints that
marking precopy complete.
Move that notification (along with the tracepoint) out to the caller, so
that postcopy will only notify once right at the start of switchover phase
from precopy. When at it, rename it to suite the file now it locates.
For precopy, there should have no functional change except the tracepoint
has a name change.
For the other two users of qemu_savevm_state_complete_precopy(), namely:
qemu_savevm_state() and qemu_savevm_live_state(): the notifier shouldn't
matter because they're not precopy at all. Now in these two contexts (aka,
"savevm", and "colo") sometimes the precopy notifiers will still be
invoked, but that's outside the scope of this patch.
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/20250114230746.3268797-12-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
This paves way for some follow up patch to modify migration states at the
end of postcopy_start(), which should better be with the BQL so that
there's no way of concurrent cancellation.
So we'll do something slightly more with BQL but they're really trivial,
hopefully nothing will really chance with this.
A side benefit is we can drop another explicit lock() in failure path.
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/20250114230746.3268797-11-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
I can't see why we must cache the state now after we avoided possible
CANCEL race: that's the only thing I can think of that can modify the
migration state concurrently with the migration thread itself. Make all
the state updates to happen always, then we don't need to cache the state
anymore.
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/20250114230746.3268797-10-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
In migration_maybe_pause() QEMU may yield BQL before waiting for a
semaphore. However it yields the BQL too early, which logically gives it
chance for the main thread to quickly take the BQL and modify the state to
CANCELLING.
To avoid such race condition from happening at all, always update the
migration states within the BQL. It'll make sure no concurrent
cancellation can ever happen.
With that, IIUC there's chance we can remove the extra parameter in
migration_maybe_pause() to update active state, but that'll be done
separately later.
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/20250114230746.3268797-9-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Precopy uses unlimited bandwidth always during switchover, it makes sense
because this is so critical and no one would like to throttle bandwidth
during the VM blackout.
OTOH, postcopy surprisingly didn't do that. There's one line that in the
middle of the postcopy switchover it tries to switch to postcopy's
specified max-postcopy-bandwidth, but even so it's somewhere in the middle
which is strange.
This patch brings the two modes to always use unlimited bandwidth for
switchover, meanwhile only apply the postcopy max bandwidth after the
switchover is completed.
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/20250114230746.3268797-8-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Do one shot cpu sync at qemu_savevm_state_complete_precopy_non_iterable(),
instead of coding it separately in two places.
Note that in the context of qemu_savevm_state_complete_precopy(), this
patch is also an optimization for postcopy path, in that we can avoid sync
cpu twice during switchover: before this patch, postcopy_start() invokes
twice on qemu_savevm_state_complete_precopy(), each of them will try to
sync CPU info. In reality, only one of them would be enough.
For background snapshot, there's no intended functional change.
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/20250114230746.3268797-7-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
This parameter is only used by one caller, which is the genuine precopy
complete path (migration_completion_precopy).
The parameter was introduced in a1fbe750fd ("migration: Fix race of image
locking between src and dst") to make sure the inactivate will happen
before EOF to make sure dest will always be able to activate the disk
properly. However there's no limitation on how early we inactivate the
disk. For precopy completion path, we can always do that as long as VM is
stopped.
Move the disk inactivate there, then we can remove this inactivate_disk
parameter in the whole call stack, because all the rest users pass in false
always.
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/20250114230746.3268797-6-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Postcopy can trigger this tracepoint twice, while only the 1st one is
valid. Avoid triggering the 2nd tracepoint just like what we do with
recording the total downtime.
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/20250114230746.3268797-5-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
postcopy_start() is the entry function that postcopy is destined to start.
It also means QEMU source will not dump VM description, aka, the JSON
writer is garbage now.
We can leave that to be cleaned up when migration completes, however when
with the JSON writer object being present, vmstate_save() will still try to
construct the JSON objects for the VM descriptions, even though it'll never
be used later if it's postcopy.
To save those cycles, release the JSON writer earlier for postcopy. Then
vmstate_save() later will be smart enough to skip the JSON object
constructions completely. It can logically reduce downtime because all
such JSON constructions happen during postcopy blackout.
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/20250114230746.3268797-4-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
QEMU machine has a property "suppress-vmdesc". When it is enabled, QEMU
will stop attaching JSON VM description at the end of the precopy migration
stream (postcopy is never affected because postcopy never attach that).
However even if it's suppressed by the user, the source QEMU will still
construct the JSON descriptions, which is a complete waste of CPU and
memory resources.
To avoid it, only create the JSON writer object if suppress-vmdesc is not
specified.
Luckily, vmstate_save() already supports vmdesc==NULL, so only a few spots
that are left to be prepared that vmdesc can be NULL now.
When at it, move the init / destroy of the JSON writer object to start /
end of the migration - the JSON writer object is a sub-struct of migration
state, and that looks like the only object that was dynamically allocated /
destroyed within migration process. Make it the same as the rest objects
that migration uses.
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/20250114230746.3268797-3-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Add the cpr-transfer migration mode, which allows the user to transfer
a guest to a new QEMU instance on the same host with minimal guest pause
time, by preserving guest RAM in place, albeit with new virtual addresses
in new QEMU, and by preserving device file descriptors. Pages that were
locked in memory for DMA in old QEMU remain locked in new QEMU, because the
descriptor of the device that locked them remains open.
cpr-transfer preserves memory and devices descriptors by sending them to
new QEMU over a unix domain socket using SCM_RIGHTS. Such CPR state cannot
be sent over the normal migration channel, because devices and backends
are created prior to reading the channel, so this mode sends CPR state
over a second "cpr" migration channel. New QEMU reads the cpr channel
prior to creating devices or backends. The user specifies the cpr channel
in the channel arguments on the outgoing side, and in a second -incoming
command-line parameter on the incoming side.
The user must start old QEMU with the the '-machine aux-ram-share=on' option,
which allows anonymous memory to be transferred in place to the new process
by transferring a memory descriptor for each ram block. Memory-backend
objects must have the share=on attribute, but memory-backend-epc is not
supported.
The user starts new QEMU on the same host as old QEMU, with command-line
arguments to create the same machine, plus the -incoming option for the
main migration channel, like normal live migration. In addition, the user
adds a second -incoming option with channel type "cpr". This CPR channel
must support file descriptor transfer with SCM_RIGHTS, i.e. it must be a
UNIX domain socket.
To initiate CPR, the user issues a migrate command to old QEMU, adding
a second migration channel of type "cpr" in the channels argument.
Old QEMU stops the VM, saves state to the migration channels, and enters
the postmigrate state. New QEMU mmap's memory descriptors, and execution
resumes.
The implementation splits qmp_migrate into start and finish functions.
Start sends CPR state to new QEMU, which responds by closing the CPR
channel. Old QEMU detects the HUP then calls finish, which connects the
main migration channel.
In summary, the usage is:
qemu-system-$arch -machine aux-ram-share=on ...
start new QEMU with "-incoming <main-uri> -incoming <cpr-channel>"
Issue commands to old QEMU:
migrate_set_parameter mode cpr-transfer
{"execute": "migrate", ...
{"channel-type": "main"...}, {"channel-type": "cpr"...} ... }
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-17-git-send-email-steven.sistare@oracle.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Extend the -incoming option to allow an @MigrationChannel to be specified.
This allows channels other than 'main' to be described on the command
line, which will be needed for CPR.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Acked-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-13-git-send-email-steven.sistare@oracle.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Export migrate_uri_parse for use outside migration internals, and define
a method migrate_is_uri that indicates when migrate_uri_parse should
be used.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-12-git-send-email-steven.sistare@oracle.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
CPR must save state that is needed after QEMU is restarted, when devices
are realized. Thus the extra state cannot be saved in the migration
channel, as objects must already exist before that channel can be loaded.
Instead, define auxilliary state structures and vmstate descriptions, not
associated with any registered object, and serialize the aux state to a
cpr-specific channel in cpr_state_save. Deserialize in cpr_state_load
after QEMU restarts, before devices are realized.
Provide accessors for clients to register file descriptors for saving.
The mechanism for passing the fd's to the new process will be specific
to each migration mode, and added in subsequent patches.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-8-git-send-email-steven.sistare@oracle.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
This patch proposes a flag to maintain disk activation status globally. It
mostly rewrites disk activation mgmt for QEMU, including COLO and QMP
command xen_save_devices_state.
Backgrounds
===========
We have two problems on disk activations, one resolved, one not.
Problem 1: disk activation recover (for switchover interruptions)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When migration is either cancelled or failed during switchover, especially
when after the disks are inactivated, QEMU needs to remember re-activate
the disks again before vm starts.
It used to be done separately in two paths: one in qmp_migrate_cancel(),
the other one in the failure path of migration_completion().
It used to be fixed in different commits, all over the places in QEMU. So
these are the relevant changes I saw, I'm not sure if it's complete list:
- In 2016, commit fe904ea824 ("migration: regain control of images when
migration fails to complete")
- In 2017, commit 1d2acc3162 ("migration: re-active images while migration
been canceled after inactive them")
- In 2023, commit 6dab4c93ec ("migration: Attempt disk reactivation in
more failure scenarios")
Now since we have a slightly better picture maybe we can unify the
reactivation in a single path.
One side benefit of doing so is, we can move the disk operation outside QMP
command "migrate_cancel". It's possible that in the future we may want to
make "migrate_cancel" be OOB-compatible, while that requires the command
doesn't need BQL in the first place. This will already do that and make
migrate_cancel command lightweight.
Problem 2: disk invalidation on top of invalidated disks
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This is an unresolved bug for current QEMU. Link in "Resolves:" at the
end. It turns out besides the src switchover phase (problem 1 above), QEMU
also needs to remember block activation on destination.
Consider two continuous migration in a row, where the VM was always paused.
In that scenario, the disks are not activated even until migration
completed in the 1st round. When the 2nd round starts, if QEMU doesn't
know the status of the disks, it needs to try inactivate the disk again.
Here the issue is the block layer API bdrv_inactivate_all() will crash a
QEMU if invoked on already inactive disks for the 2nd migration. For
detail, see the bug link at the end.
Implementation
==============
This patch proposes to maintain disk activation with a global flag, so we
know:
- If we used to inactivate disks for migration, but migration got
cancelled, or failed, QEMU will know it should reactivate the disks.
- On incoming side, if the disks are never activated but then another
migration is triggered, QEMU should be able to tell that inactivate is
not needed for the 2nd migration.
We used to have disk_inactive, but it only solves the 1st issue, not the
2nd. Also, it's done in completely separate paths so it's extremely hard
to follow either how the flag changes, or the duration that the flag is
valid, and when we will reactivate the disks.
Convert the existing disk_inactive flag into that global flag (also invert
its naming), and maintain the disk activation status for the whole
lifecycle of qemu. That includes the incoming QEMU.
Put both of the error cases of source migration (failure, cancelled)
together into migration_iteration_finish(), which will be invoked for
either of the scenario. So from that part QEMU should behave the same as
before. However with such global maintenance on disk activation status, we
not only cleanup quite a few temporary paths that we try to maintain the
disk activation status (e.g. in postcopy code), meanwhile it fixes the
crash for problem 2 in one shot.
For freshly started QEMU, the flag is initialized to TRUE showing that the
QEMU owns the disks by default.
For incoming migrated QEMU, the flag will be initialized to FALSE once and
for all showing that the dest QEMU doesn't own the disks until switchover.
That is guaranteed by the "once" variable.
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2395
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Message-Id: <20241206230838.1111496-7-peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Src QEMU sets block_inactive=true very early before the invalidation takes
place. It means if something wrong happened during setting the flag but
before reaching qemu_savevm_state_complete_precopy_non_iterable() where it
did the invalidation work, it'll make block_inactive flag inconsistent.
For example, think about when qemu_savevm_state_complete_precopy_iterable()
can fail: it will have block_inactive set to true even if all block drives
are active.
Fix that by only update the flag after the invalidation is done.
No Fixes for any commit, because it's not an issue if bdrv_activate_all()
is re-entrant upon all-active disks - false positive block_inactive can
bring nothing more than "trying to active the blocks but they're already
active". However let's still do it right to avoid the inconsistent flag
v.s. reality.
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Message-Id: <20241206230838.1111496-6-peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Migration capability 'late-block-active' controls when the block drives
will be activated. If enabled, block drives will only be activated until
VM starts, either src runstate was "live" (RUNNING, or SUSPENDED), or it'll
be postponed until qmp_cont().
Let's do this unconditionally. There's no harm to delay activation of
block drives. Meanwhile there's no ABI breakage if dest does it, because
src QEMU has nothing to do with it, so it's no concern on ABI breakage.
IIUC we could avoid introducing this cap when introducing it before, but
now it's still not too late to just always do it. Cap now prone to
removal, but it'll be for later patches.
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Message-Id: <20241206230838.1111496-4-peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
In 99% cases, after QEMU migrates to dest host, it tries to detect the
target VM runstate using global_state_get_runstate().
There's one outlier so far which is Xen that won't send global state.
That's the major reason why global_state_received() check was always there
together with global_state_get_runstate().
However it's utterly confusing why global_state_received() has anything to
do with "let's start VM or not".
Provide a helper to explain it, then we have an unified entry for getting
the target dest QEMU runstate after migration.
Suggested-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20241206230838.1111496-2-peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
After being removed from VFIO and dirty limit, migration_is_active() no
longer has any users outside the migration subsystem, and in fact, it's
only used in migration.c.
Unexport it and also relocate it so it can be made static.
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Tested-by: Joao Martins <joao.m.martins@oracle.com>
Link: https://lore.kernel.org/r/20241218134022.21264-8-avihaih@nvidia.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
After being removed from VFIO, migration_is_device() no longer has any
users. Drop it.
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Tested-by: Joao Martins <joao.m.martins@oracle.com>
Link: https://lore.kernel.org/r/20241218134022.21264-7-avihaih@nvidia.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Headers in include/sysemu/ are not only related to system
*emulation*, they are also used by virtualization. Rename
as system/ which is clearer.
Files renamed manually then mechanical change using sed tool.
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Lei Yang <leiyang@redhat.com>
Message-Id: <20241203172445.28576-1-philmd@linaro.org>
Export the migration_properties array size from options.c;
use that to feed device_class_set_props_n. We must remove
DEFINE_PROP_END_OF_LIST so the count is correct.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Lei Yang <leiyang@redhat.com>
Link: https://lore.kernel.org/r/20241218134251.4724-15-richard.henderson@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a macro expansion of device_class_set_props which can check
on the type and size of PROPS before calling the function.
Avoid the macro in migration.c because migration_properties
is defined externally with indeterminate size.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Lei Yang <leiyang@redhat.com>
Link: https://lore.kernel.org/r/20241218134251.4724-13-richard.henderson@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Report shows that commit 34a8892dec broke iotest 055:
https://lore.kernel.org/r/b8806360-a2b6-4608-83a3-db67e264c733@linaro.org
Denis Rastyogin reported more such issue:
https://lore.kernel.org/r/20241107114256.106831-1-gerben@altlinux.org
In this merge, the migration_is_idle() function was replaced with
migrate_is_running(). However, the null pointer check for `s` was
removed, leading to a dereference of `s` when using qemu-system-x86_64
-hda *.vdi.
When replacing migration_is_idle() with "!migration_is_running()", it was
overlooked that the idle helper also checks for current_migration being
available first. Sample stack dump:
migration_is_running
is_busy
migrate_add_blocker_modes
migrate_add_blocker_normal
vmdk_open
bdrv_open_driver
bdrv_open_common
bdrv_open_inherit
bdrv_open
blk_new_open
blockdev_init
drive_new
drive_init_func
qemu_opts_foreach
configure_blockdev
qemu_create_early_backends
qemu_init
main
The check would be there if the whole series was applied, but since the
last patches in the previous series rely on some other patches to land
first, we need to recover the behavior of migration_is_idle() first before
that whole set will be merged.
I left migration_is_active / migration_is_device alone, as I don't think
it's possible for them to hit uninitialized current_migration. Also they're
prone to removal soon from VFIO side.
Cc: Peter Maydell <peter.maydell@linaro.org>
Fixes: 34a8892dec ("migration: Drop migration_is_idle()")
Reported-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reported-by: Denis Rastyogin <gerben@altlinux.org>
Tested-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Tested-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20241105182725.2393425-1-peterx@redhat.com
[peterx: enhance commit msg]
Signed-off-by: Peter Xu <peterx@redhat.com>
Now with the current migration_is_running(), it will report exactly the
opposite of what will be reported by migration_is_idle().
Drop migration_is_idle(), instead use "!migration_is_running()" which
should be identical on functionality.
In reality, most of the idle check is inverted, so it's even easier to
write with "migrate_is_running()" check.
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20241024213056.1395400-6-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
This helper is mostly the same as migration_is_running(), except that one
has COLO reported as true, the other has CANCELLING reported as true.
Per my past years experience on the state changes, none of them should
matter.
To make it slightly safer, report both COLO || CANCELLING to be true in
migration_is_running(), then drop the other one. We kept the 1st only
because the name is simpler, and clear enough.
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20241024213056.1395400-5-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Both migration thread or background snapshot thread will take a refcount of
the migration object at the entrace of the thread function.
That makes sense, because it protects the object from being freed by the
main thread in migration_shutdown() later, but it might still race with it
if the thread is scheduled too late. Consider the case right after
pthread_create() happened, VM shuts down with the object released, but
right after that the migration thread finally got created, referencing
MigrationState* in the opaque pointer which is already freed.
The only 100% safe way to make sure it won't get freed is taking the
refcount right before the thread is created, meanwhile when BQL is held.
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20241024213056.1395400-2-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
When VM is configured with huge memory, the current throttle logic
doesn't look like to scale, because migration_trigger_throttle()
is only called for each iteration, so it won't be invoked for a long
time if one iteration can take a long time.
The periodic dirty sync aims to fix the above issue by synchronizing
the ramblock from remote dirty bitmap and, when necessary, triggering
the CPU throttle multiple times during a long iteration.
This is a trade-off between synchronization overhead and CPU throttle
impact.
Signed-off-by: Hyman Huang <yong.huang@smartx.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/f61f1b3653f2acf026901103e1c73d157d38b08f.1729146786.git.yong.huang@smartx.com
[peterx: make prev_cnt global, and reset for each migration]
Signed-off-by: Peter Xu <peterx@redhat.com>
Move cpu-throttle.c from system to migration since it's
only used for migration; this makes us avoid exporting the
util functions and variables in misc.h but export them in
migration.h when implementing the periodic ramblock dirty
sync feature in the upcoming commits.
Since CPU throttle timers are only used in migration, move
their registry to migration_object_init.
Signed-off-by: Hyman Huang <yong.huang@smartx.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/c1b3efaa0cb49e03d422e9da97bdb65cc3d234d1.1729146786.git.yong.huang@smartx.com
[peterx: Fix build on MacOS on cocoa.m, not move cpu-throttle.h yet]
[peterx: Fix subject spelling, per pm215]
Signed-off-by: Peter Xu <peterx@redhat.com>
Keep migration thread names together, so it's easier to see a list of all
possible migration threads.
Still two functional changes below besides the macro defintions:
- There's one dirty rate thread that we overlooked before, now we add
that too and name it as "mig/dirtyrate" following the old rules.
- The old name "mig/src/rp-thr" has "-thr" but it may not be useful if
it's a thread name anyway, while "rp" can be slightly hard to read.
Taking this chance to rename it to "mig/src/return", hopefully a better
name.
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Acked-by: Hyman Huang <yong.huang@smartx.com>
Reviewed-by: Zhang Chen <chen.zhang@intel.com>
Link: https://lore.kernel.org/r/20241011153652.517440-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
The cleanup function can in many cases needs cleanup on its own.
The major thing we want to do here is not referencing to_dst_file when
without the file mutex. When at it, touch things elsewhere too to make it
look slightly better in general.
One thing to mention is, migration_thread has its own "running" boolean, so
it doesn't need to rely on to_dst_file being non-NULL. Multifd has a
dependency so it needs to be skipped if to_dst_file is not yet set; add a
richer comment for such reason.
Resolves: Coverity CID 1527402
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240919163042.116767-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
../migration/dirtyrate.c:186:5: error: ‘records’ may be used uninitialized [-Werror=maybe-uninitialized]
../migration/dirtyrate.c:168:12: error: ‘gen_id’ may be used uninitialized [-Werror=maybe-uninitialized]
../migration/migration.c:2273:5: error: ‘file’ may be used uninitialized [-Werror=maybe-uninitialized]
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Hyman Huang <yong.huang@smartx.com>
Fix a segmentation fault in multifd when rb->receivedmap is cleared
too early.
After commit 5ef7e26bdb ("migration/multifd: solve zero page causing
multiple page faults"), multifd started using the rb->receivedmap
bitmap, which belongs to ram.c and is initialized and *freed* from the
ram SaveVMHandlers.
Multifd threads are live until migration_incoming_state_destroy(),
which is called after qemu_loadvm_state_cleanup(), leading to a crash
when accessing rb->receivedmap.
process_incoming_migration_co() ...
qemu_loadvm_state() multifd_nocomp_recv()
qemu_loadvm_state_cleanup() ramblock_recv_bitmap_set_offset()
rb->receivedmap = NULL set_bit_atomic(..., rb->receivedmap)
...
migration_incoming_state_destroy()
multifd_recv_cleanup()
multifd_recv_terminate_threads(NULL)
Move the loadvm cleanup into migration_incoming_state_destroy(), after
multifd_recv_cleanup() to ensure multifd threads have already exited
when rb->receivedmap is cleared.
Adjust the postcopy listen thread comment to indicate that we still
want to skip the cpu synchronization.
CC: qemu-stable@nongnu.org
Fixes: 5ef7e26bdb ("migration/multifd: solve zero page causing multiple page faults")
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240917185802.15619-3-farosas@suse.de
[peterx: added comment in migration_incoming_state_destroy()]
Signed-off-by: Peter Xu <peterx@redhat.com>
This patch adds a migration state on src called "postcopy-recover-setup".
The new state will describe the intermediate step starting from when the
src QEMU received a postcopy recovery request, until the migration channels
are properly established, but before the recovery process take place.
The request came from Libvirt where Libvirt currently rely on the migration
state events to detect migration state changes. That works for most of the
migration process but except postcopy recovery failures at the beginning.
Currently postcopy recovery only has two major states:
- postcopy-paused: this is the state that both sides of QEMU will be in
for a long time as long as the migration channel was interrupted.
- postcopy-recover: this is the state where both sides of QEMU handshake
with each other, preparing for a continuation of postcopy which used to
be interrupted.
The issue here is when the recovery port is invalid, the src QEMU will take
the URI/channels, noticing the ports are not valid, and it'll silently keep
in the postcopy-paused state, with no event sent to Libvirt. In this case,
the only thing Libvirt can do is to poll the migration status with a proper
interval, however that's less optimal.
Considering that this is the only case where Libvirt won't get a
notification from QEMU on such events, let's add postcopy-recover-setup
state to mimic what we have with the "setup" state of a newly initialized
migration, describing the phase of connection establishment.
With that, postcopy recovery will have two paths to go now, and either path
will guarantee an event generated. Now the events will look like this
during a recovery process on src QEMU:
- Initially when the recovery is initiated on src, QEMU will go from
"postcopy-paused" -> "postcopy-recover-setup". Old QEMUs don't have
this event.
- Depending on whether the channel re-establishment is succeeded:
- In succeeded case, src QEMU will move from "postcopy-recover-setup"
to "postcopy-recover". Old QEMUs also have this event.
- In failure case, src QEMU will move from "postcopy-recover-setup" to
"postcopy-paused" again. Old QEMUs don't have this event.
This guarantees that Libvirt will always receive a notification for
recovery process properly.
One thing to mention is, such new status is only needed on src QEMU not
both. On dest QEMU, the state machine doesn't change. Hence the events
don't change either. It's done like so because dest QEMU may not have an
explicit point of setup start. E.g., it can happen that when dest QEMUs
doesn't use migrate-recover command to use a new URI/channel, but the old
URI/channels can be reused in recovery, in which case the old ports simply
can work again after the network routes are fixed up.
Add a new helper postcopy_is_paused() detecting whether postcopy is still
paused, taking RECOVER_SETUP into account too. When using it on both
src/dst, a slight change is done altogether to always wait for the
semaphore before checking the status, because for both sides a sem_post()
will be required for a recovery.
Cc: Jiri Denemark <jdenemar@redhat.com>
Cc: Prasad Pandit <ppandit@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Buglink: https://issues.redhat.com/browse/RHEL-38485
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Destination QEMU can setup incoming ports for two purposes: either a fresh
new incoming migration, in which QEMU will switch to SETUP for channel
establishment, or a paused postcopy migration, in which QEMU will stay in
POSTCOPY_PAUSED until kicking off the RECOVER phase.
Now the state machine worked on dest node for the latter, only because
migrate_set_state() implicitly will become a noop if the current state
check failed. It wasn't clear at all.
Clean it up by providing a helper migration_incoming_state_setup() doing
proper checks over current status. Postcopy-paused will be explicitly
checked now, and then we can bail out for unknown states.
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
QEMU uses "int" in most cases even if it stores MigrationStatus. I don't
know why, so let's try to do that right and see what blows up..
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
The postcopy thread names on dest QEMU are slightly confusing, partly I'll
need to blame myself on 36f62f11e4 ("migration: Postcopy preemption
preparation on channel creation"). E.g., "fault-fast" reads like a fast
version of "fault-default", but it's actually the fast version of
"postcopy/listen".
Taking this chance, rename all the migration threads with proper rules.
Considering we only have 15 chars usable, prefix all threads with "mig/",
meanwhile identify src/dst threads properly this time. So now most thread
names will look like "mig/DIR/xxx", where DIR will be "src"/"dst", except
the bg-snapshot thread which doesn't have a direction.
For multifd threads, making them "mig/{src|dst}/{send|recv}_%d".
We used to have "live_migration" thread for a very long time, now it's
called "mig/src/main". We may hope to have "mig/dst/main" soon but not
yet.
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Zhijian Li (Fujitsu) <lizhijian@fujitsu.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
