This patch adds the new VM state change cb type `VMChangeStateHandlerWithRet`,
which has return value for `VMChangeStateEntry`.
Thus, we can register a new VM state change cb with return value for device.
Note that `VMChangeStateHandler` and `VMChangeStateHandlerWithRet` are mutually
exclusive and cannot be provided at the same time.
This patch is the pre patch for 'vhost-user: return failure if backend crashes
when live migration', which makes the live migration aware of the loss of
connection with the vhost-user backend and aborts the live migration.
Virtio device will use VMChangeStateHandlerWithRet.
Signed-off-by: Haoqian He <haoqian.he@smartx.com>
Message-Id: <20250416024729.3289157-2-haoqian.he@smartx.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
"hw/vfio/vfio-common.h" has been emptied of most of its declarations
by the previous changes and the only declarations left are related to
VFIODevice. Rename it to "hw/vfio/vfio-device.h" and make the
necessary adjustments.
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Link: https://lore.kernel.org/qemu-devel/20250326075122.1299361-36-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
These routines are migration related. Move their declaration and
implementation under the migration files.
Reviewed-by: Prasad Pandit <pjp@fedoraproject.org>
Reviewed-by: John Levon <john.levon@nutanix.com>
Link: https://lore.kernel.org/qemu-devel/20250326075122.1299361-8-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
The migration core subsystem makes use of the VFIO migration API to
collect statistics on the number of bytes transferred. These services
are declared in "hw/vfio/vfio-common.h" which also contains VFIO
internal declarations. Move the migration declarations into a new
header file "hw/vfio/vfio-migration.h" to reduce the exposure of VFIO
internals.
While at it, use a 'vfio_migration_' prefix for these services.
To be noted, vfio_migration_add_bytes_transferred() is a VFIO
migration internal service which we will be moved in the subsequent
patches.
Cc: Kirti Wankhede <kwankhede@nvidia.com>
Cc: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Prasad Pandit <pjp@fedoraproject.org>
Reviewed-by: John Levon <john.levon@nutanix.com>
Reviewed-by: Avihai Horon <avihaih@nvidia.com>
Link: https://lore.kernel.org/qemu-devel/20250326075122.1299361-4-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Implement the multifd device state transfer via additional per-device
thread inside save_live_complete_precopy_thread handler.
Switch between doing the data transfer in the new handler and doing it
in the old save_state handler depending if VFIO multifd transfer is enabled
or not.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/4d727e2e0435e0022d50004e474077632830e08d.1741124640.git.maciej.szmigiero@oracle.com
[ clg: - Reordered savevm_vfio_handlers
- Updated save_live_complete_precopy* documentation ]
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Add a thread which loads the VFIO device state buffers that were received
via multifd.
Each VFIO device that has multifd device state transfer enabled has one
such thread, which is created using migration core API
qemu_loadvm_start_load_thread().
Since it's important to finish loading device state transferred via the
main migration channel (via save_live_iterate SaveVMHandler) before
starting loading the data asynchronously transferred via multifd the thread
doing the actual loading of the multifd transferred data is only started
from switchover_start SaveVMHandler.
switchover_start handler is called when MIG_CMD_SWITCHOVER_START
sub-command of QEMU_VM_COMMAND is received via the main migration channel.
This sub-command is only sent after all save_live_iterate data have already
been posted so it is safe to commence loading of the multifd-transferred
device state upon receiving it - loading of save_live_iterate data happens
synchronously in the main migration thread (much like the processing of
MIG_CMD_SWITCHOVER_START) so by the time MIG_CMD_SWITCHOVER_START is
processed all the proceeding data must have already been loaded.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/9abe612d775aaf42e31646796acd2363c723a57a.1741124640.git.maciej.szmigiero@oracle.com
[ clg: - Reordered savevm_vfio_handlers
- Added switchover_start documentation ]
Signed-off-by: Cédric Le Goater <clg@redhat.com>
The multifd received data needs to be reassembled since device state
packets sent via different multifd channels can arrive out-of-order.
Therefore, each VFIO device state packet carries a header indicating its
position in the stream.
The raw device state data is saved into a VFIOStateBuffer for later
in-order loading into the device.
The last such VFIO device state packet should have
VFIO_DEVICE_STATE_CONFIG_STATE flag set and carry the device config state.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/e3bff515a8d61c582b94b409eb12a45b1a143a69.1741124640.git.maciej.szmigiero@oracle.com
[ clg: - Reordered savevm_vfio_handlers
- Added load_state_buffer documentation ]
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Add basic types and flags used by VFIO multifd device state transfer
support.
Since we'll be introducing a lot of multifd transfer specific code,
add a new file migration-multifd.c to home it, wired into main VFIO
migration code (migration.c) via migration-multifd.h header file.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/4eedd529e6617f80f3d6a66d7268a0db2bc173fa.1741124640.git.maciej.szmigiero@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
So it can be safety accessed from multiple threads.
This variable type needs to be changed to unsigned long since
32-bit host platforms lack the necessary addition atomics on 64-bit
variables.
Using 32-bit counters on 32-bit host platforms should not be a problem
in practice since they can't realistically address more memory anyway.
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Link: https://lore.kernel.org/qemu-devel/dc391771d2d9ad0f311994f0cb9e666da564aeaf.1741124640.git.maciej.szmigiero@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
And rename existing load_device_config_state trace event to
load_device_config_state_end for consistency since it is triggered at the
end of loading of the VFIO device config state.
This way both the start and end points of particular device config
loading operation (a long, BQL-serialized operation) are known.
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Link: https://lore.kernel.org/qemu-devel/1b6c5a2097e64c272eb7e53f9e4cca4b79581b38.1741124640.git.maciej.szmigiero@oracle.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>
This way both the start and end points of migrating a particular VFIO
device are known.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
vfio_state_pending_exact() is used to update migration core how much
device data is left for the device migration. Currently, the sum of
pre-copy and stop-copy sizes of the VFIO device are reported.
The pre-copy size is obtained via the VFIO_MIG_GET_PRECOPY_INFO ioctl,
which returns the amount of device data available to be transferred
while the device is in the PRE_COPY states.
The stop-copy size is obtained via the VFIO_DEVICE_FEATURE_MIG_DATA_SIZE
ioctl, which returns the total amount of device data left to be
transferred in order to complete the device migration.
According to the above, current implementation is wrong -- it reports
extra overlapping data because pre-copy size is already contained in
stop-copy size. Fix it by reporting only stop-copy size.
Fixes: eda7362af9 ("vfio/migration: Add VFIO migration pre-copy support")
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
QAPI's 'prefix' feature can make the connection between enumeration
type and its constants less than obvious. It's best used with
restraint.
VfioMigrationState has a 'prefix' that overrides the generated
enumeration constants' prefix to QAPI_VFIO_MIGRATION_STATE.
We could simply drop 'prefix', but then the enumeration constants
would look as if they came from kernel header linux/vfio.h.
Rename the type to QapiVfioMigrationState instead, so that 'prefix' is
not needed.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240904111836.3273842-20-armbru@redhat.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
The property 'x-pre-copy-dirty-page-tracking' allows disabling the whole
tracking of VF pre-copy phase of dirty page tracking, though it means
that it will only be used at the start of the switchover phase.
Add an option that disables the VF dirty page tracking, and fall
back into container-based dirty page tracking. This also allows to
use IOMMU dirty tracking even on VFs with their own dirty
tracker scheme.
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
By default VFIO migration is set to auto, which will support live
migration if the migration capability is set *and* also dirty page
tracking is supported.
For testing purposes one can force enable without dirty page tracking
via enable-migration=on, but that option is generally left for testing
purposes.
So starting with IOMMU dirty tracking it can use to accommodate the lack of
VF dirty page tracking allowing us to minimize the VF requirements for
migration and thus enabling migration by default for those too.
While at it change the error messages to mention IOMMU dirty tracking as
well.
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
[ clg: - spelling in commit log ]
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Move trace_vfio_migration_set_state() to the top of the function, add
recover_state to it, and add a new trace event to
vfio_migration_set_device_state().
This improves tracing of device state changes as state changes are now
also logged when vfio_migration_set_state() fails (covering recover
state and device reset transitions) and in no-op state transitions to
the same state.
Suggested-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
When migrating a VFIO device that supports pre-copy, it is transitioned
to STOP_COPY twice: once in vfio_vmstate_change() and second time in
vfio_save_complete_precopy().
The second transition is harmless, as it's a STOP_COPY->STOP_COPY no-op
transition. However, with the newly added VFIO migration QAPI event, the
STOP_COPY event is undesirably emitted twice.
Prevent this by returning early in vfio_migration_set_state() if
new_state is the same as current device state.
Note that the STOP_COPY transition in vfio_save_complete_precopy() is
essential for VFIO devices that don't support pre-copy, for migrating an
already stopped guest and for snapshots.
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Emit VFIO migration QAPI event when a VFIO device changes its migration
state. This can be used by management applications to get updates on the
current state of the VFIO device for their own purposes.
A new per VFIO device capability, "migration-events", is added so events
can be enabled only for the required devices. It is disabled by default.
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
vfio_save_complete_precopy() currently returns before doing the trace
event. Change that.
Reviewed-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Use vmstate_save_state_with_err() to improve error reporting in the
callers and store a reported error under the migration stream. Add
documentation while at it.
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Avihai Horon <avihaih@nvidia.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Add an Error** argument to vfio_migration_set_state() and adjust
callers, including vfio_save_setup(). The error will be propagated up
to qemu_savevm_state_setup() where the save_setup() handler is
executed.
Modify vfio_vmstate_change_prepare() and vfio_vmstate_change() to
store a reported error under the migration stream if a migration is in
progress.
Reviewed-by: Avihai Horon <avihaih@nvidia.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Use it to update the current error of the migration stream if
available and if not, simply print out the error. Next changes will
update with an error to report.
Reviewed-by: Avihai Horon <avihaih@nvidia.com>
Acked-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
This will be useful to report errors at a higher level, mostly in VFIO
today.
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20240320064911.545001-9-clg@redhat.com
[peterx: drop comment for ERRP_GUARD, per Markus]
Signed-off-by: Peter Xu <peterx@redhat.com>
The purpose is to record a potential error in the migration stream if
qemu_savevm_state_setup() fails. Most of the current .save_setup()
handlers can be modified to use the Error argument instead of managing
their own and calling locally error_report().
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Harsh Prateek Bora <harshpb@linux.ibm.com>
Cc: Halil Pasic <pasic@linux.ibm.com>
Cc: Thomas Huth <thuth@redhat.com>
Cc: Eric Blake <eblake@redhat.com>
Cc: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Cc: John Snow <jsnow@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20240320064911.545001-8-clg@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
This will prepare ground for future changes adding an Error** argument
to the save_setup() handler. We need to make sure that on failure,
vfio_save_setup() always sets a new error.
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20240320064911.545001-3-clg@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
- Avihai's fix to allow vmstate iterators to not starve for VFIO
- Maksim's fix on additional check on precopy load error
- Fabiano's fix on fdatasync() hang in mapped-ram
- Jonathan's fix on vring cached access over MMIO regions
- Cedric's cleanup patches 1-4 out of his error report series
- Yu's fix for RDMA migration (which used to be broken even for 8.2)
- Anthony's small cleanup/fix on err message
- Steve's patches on privatize migration.h
- Xiang's patchset to enable zero page detections in multifd threads
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Merge tag 'migration-20240311-pull-request' of https://gitlab.com/peterx/qemu into staging
Migration pull request
- Avihai's fix to allow vmstate iterators to not starve for VFIO
- Maksim's fix on additional check on precopy load error
- Fabiano's fix on fdatasync() hang in mapped-ram
- Jonathan's fix on vring cached access over MMIO regions
- Cedric's cleanup patches 1-4 out of his error report series
- Yu's fix for RDMA migration (which used to be broken even for 8.2)
- Anthony's small cleanup/fix on err message
- Steve's patches on privatize migration.h
- Xiang's patchset to enable zero page detections in multifd threads
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# gpg: Signature made Mon 11 Mar 2024 21:59:20 GMT
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* tag 'migration-20240311-pull-request' of https://gitlab.com/peterx/qemu: (34 commits)
migration/multifd: Add new migration test cases for legacy zero page checking.
migration/multifd: Enable multifd zero page checking by default.
migration/multifd: Implement ram_save_target_page_multifd to handle multifd version of MigrationOps::ram_save_target_page.
migration/multifd: Implement zero page transmission on the multifd thread.
migration/multifd: Add new migration option zero-page-detection.
migration/multifd: Allow clearing of the file_bmap from multifd
migration/multifd: Allow zero pages in file migration
migration: purge MigrationState from public interface
migration: delete unused accessors
migration: privatize colo interfaces
migration: migration_file_set_error
migration: migration_is_device
migration: migration_thread_is_self
migration: export vcpu_dirty_limit_period
migration: export migration_is_running
migration: export migration_is_active
migration: export migration_is_setup_or_active
migration: remove migration.h references
migration: export fewer options
migration: Fix format in error message
...
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
A small number of migration options are accessed by migration clients,
but to see them clients must include all of options.h, which is mostly
for migration core code. migrate_mode() in particular will be needed by
multiple clients.
Refactor the option declarations so clients can see the necessary few via
misc.h, which already exports a portion of the client API.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Link: https://lore.kernel.org/r/1710179319-294320-1-git-send-email-steven.sistare@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>
VFIO migration buffer size is currently limited to 1MB. Therefore, there
is no need to check if migration rate exceeded, as in the worst case it
will exceed by only 1MB.
However, if the buffer size is later changed to a bigger value,
vfio_save_iterate() should enforce migration rate (similar to migration
RAM code).
Add a note about this in vfio_save_iterate() to serve as a reminder.
Suggested-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240304105339.20713-4-avihaih@nvidia.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Currently, vfio_save_state() returns 1 regardless of whether there is
more data to send or not. This was done to prevent a fast changing VFIO
device from potentially blocking other devices from sending their data,
as qemu_savevm_state_iterate() serialized devices.
Now that qemu_savevm_state_iterate() no longer serializes devices, there
is no need for that.
Refactor vfio_save_state() to return 0 if more data is available and 1
if no more data is available.
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240304105339.20713-3-avihaih@nvidia.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Allow cpr-reboot for vfio if the guest is in the suspended runstate. The
guest drivers' suspend methods flush outstanding requests and re-initialize
the devices, and thus there is no device state to save and restore. The
user is responsible for suspending the guest before initiating cpr, such as
by issuing guest-suspend-ram to the qemu guest agent.
Relax the vfio blocker so it does not apply to cpr, and add a notifier that
verifies the guest is suspended.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Define MigrationNotifyFunc to improve type safety and simplify migration
notifiers.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/1708622920-68779-7-git-send-email-steven.sistare@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Passing MigrationState to notifiers is unsound because they could access
unstable migration state internals or even modify the state. Instead, pass
the minimal info needed in a new MigrationEvent struct, which could be
extended in the future if needed.
Suggested-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/1708622920-68779-5-git-send-email-steven.sistare@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Change all migration notifiers to type NotifierWithReturn, so notifiers
can return an error status in a future patch. For now, pass NULL for the
notifier error parameter, and do not check the return value.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/1708622920-68779-4-git-send-email-steven.sistare@oracle.com
[peterx: dropped unexpected update to roms/seabios-hppa]
Signed-off-by: Peter Xu <peterx@redhat.com>
There are several places where failure in setting the device state leads
to a device reset, which is done by setting ERROR as the recover state.
Add a helper function that sets the device state and resets the device
in case of failure. This will make the code cleaner and remove duplicate
comments.
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Pass the callback function to add_migration_state_change_notifier so
that migration can initialize the notifier on add and clear it on
delete, which simplifies the call sites. Shorten the function names
so the extra arg can be added more legibly. Hide the global notifier
list in a new function migration_call_notifiers, and make it externally
visible so future live update code can call it.
No functional change.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Tested-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <1686148954-250144-1-git-send-email-steven.sistare@oracle.com>
Modify migrate_add_blocker and migrate_del_blocker to take an Error **
reason. This allows migration to own the Error object, so that if
an error occurs in migrate_add_blocker, migration code can free the Error
and clear the client handle, simplifying client code. It also simplifies
the migrate_del_blocker call site.
In addition, this is a pre-requisite for a proposed future patch that would
add a mode argument to migration requests to support live update, and
maintain a list of blockers for each mode. A blocker may apply to a single
mode or to multiple modes, and passing Error** will allow one Error object
to be registered for multiple modes.
No functional change.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Tested-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <1697634216-84215-1-git-send-email-steven.sistare@oracle.com>
Background snapshot allows creating a snapshot of the VM while it's
running and keeping it small by not including dirty RAM pages.
The way it works is by first stopping the VM, saving the non-iterable
devices' state and then starting the VM and saving the RAM while write
protecting it with UFFD. The resulting snapshot represents the VM state
at snapshot start.
VFIO migration is not compatible with background snapshot.
First of all, VFIO device state is not even saved in background snapshot
because only non-iterable device state is saved. But even if it was
saved, after starting the VM, a VFIO device could dirty pages without it
being detected by UFFD write protection. This would corrupt the
snapshot, as the RAM in it would not represent the RAM at snapshot
start.
To prevent this, block VFIO migration with background snapshot.
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
