The file migration code was allowing a possible -1 from a failed call
to dup() to propagate into the new QIOFileChannel::fd before checking
for validity. Coverity doesn't like that, possibly due to the the
lseek(-1, ...) call that would ensue before returning from the channel
creation routine.
Use the newly introduced qio_channel_file_dupfd() to properly check
the return of dup() before proceeding.
Fixes: CID 1539961
Fixes: CID 1539965
Fixes: CID 1539960
Fixes: 2dd7ee7a51 ("migration/multifd: Add incoming QIOChannelFile support")
Fixes: decdc76772 ("migration/multifd: Add mapped-ram support to fd: URI")
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: "Daniel P. Berrangé" <berrange@redhat.com>
Link: https://lore.kernel.org/r/20240311233335.17299-3-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
1. Set default "zero-page-detection" option to "multifd". Now
zero page checking can be done in the multifd threads and this
becomes the default configuration.
2. Handle migration QEMU9.0 -> QEMU8.2 compatibility. We provide
backward compatibility where zero page checking is done from the
migration main thread.
Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/20240311180015.3359271-7-hao.xiang@linux.dev
Signed-off-by: Peter Xu <peterx@redhat.com>
1. Add a dedicated handler for MigrationOps::ram_save_target_page in
multifd live migration.
2. Refactor ram_save_target_page_legacy so that the legacy and multifd
handlers don't have internal functions calling into each other.
Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Message-Id: <20240226195654.934709-4-hao.xiang@bytedance.com>
Link: https://lore.kernel.org/r/20240311180015.3359271-6-hao.xiang@linux.dev
Signed-off-by: Peter Xu <peterx@redhat.com>
1. Add zero_pages field in MultiFDPacket_t.
2. Implements the zero page detection and handling on the multifd
threads for non-compression, zlib and zstd compression backends.
3. Added a new value 'multifd' in ZeroPageDetection enumeration.
4. Adds zero page counters and updates multifd send/receive tracing
format to track the newly added counters.
Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240311180015.3359271-5-hao.xiang@linux.dev
Signed-off-by: Peter Xu <peterx@redhat.com>
This new parameter controls where the zero page checking is running.
1. If this parameter is set to 'legacy', zero page checking is
done in the migration main thread.
2. If this parameter is set to 'none', zero page checking is disabled.
Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Link: https://lore.kernel.org/r/20240311180015.3359271-4-hao.xiang@linux.dev
Signed-off-by: Peter Xu <peterx@redhat.com>
We currently only need to clear the mapped-ram file bitmap from the
migration thread during save_zero_page.
We're about to add support for zero page detection on the multifd
thread, so allow ramblock_set_file_bmap_atomic() to also clear the
bits.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240311180015.3359271-3-hao.xiang@linux.dev
Signed-off-by: Peter Xu <peterx@redhat.com>
Currently, it's an error to have no data pages in the multifd file
migration because zero page detection is done in the migration thread
and zero pages don't reach multifd. This is enforced with the
pages->num assert.
We're about to add zero page detection on the multifd thread. Fix the
file_write_ramblock_iov() to stop considering p->iovs_num=0 an error.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240311180015.3359271-2-hao.xiang@linux.dev
Signed-off-by: Peter Xu <peterx@redhat.com>
Delete the MigrationState parameter from migration_is_setup_or_active
and move it to the public API in misc.h.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Link: https://lore.kernel.org/r/1710179338-294359-3-git-send-email-steven.sistare@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>
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>
In file_write_ramblock_iov(), "offset" is "uintptr_t" and not
"ram_addr_t". While usually they are both equivalent, this is not the
case with CONFIG_XEN_BACKEND.
Use the right format. This will fix build on 32-bit.
Fixes: f427d90b98 ("migration/multifd: Support outgoing mapped-ram stream format")
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Link: https://lore.kernel.org/r/20240311123439.16844-1-anthony.perard@citrix.com
Signed-off-by: Peter Xu <peterx@redhat.com>
In commit 3fa9642ff7 change was made to convert the RDMA backend to
accept MigrateAddress struct. However, the assignment of "host" leads
to data corruption on the target host and the failure of migration.
isock->host = rdma->host;
By allocating the memory explicitly for it with g_strdup_printf(), the
issue is fixed and the migration doesn't fail any more.
Fixes: 3fa9642ff7 ("migration: convert rdma backend to accept MigrateAddress")
Cc: qemu-stable <qemu-stable@nongnu.org>
Cc: Li Zhijian <lizhijian@fujitsu.com>
Link: https://lore.kernel.org/r/CAHEcVy4L_D6tuhJ8h=xLR4WaPaprJE3nnxZAEyUnoTrxQ6CF5w@mail.gmail.com
Signed-off-by: Yu Zhang <yu.zhang@ionos.com>
[peterx: use g_strdup() instead of g_strdup_printf(), per Zhijian]
Signed-off-by: Peter Xu <peterx@redhat.com>
Commit bc38feddeb ("io: fsync before closing a file channel") added a
fsync/fdatasync at the closing point of the QIOChannelFile to ensure
integrity of the migration stream in case of QEMU crash.
The decision to do the sync at qio_channel_close() was not the best
since that function runs in the main thread and the fsync can cause
QEMU to hang for several minutes, depending on the migration size and
disk speed.
To fix the hang, remove the fsync from qio_channel_file_close().
At this moment, the migration code is the only user of the fsync and
we're taking the tradeoff of not having a sync at all, leaving the
responsibility to the upper layers.
Fixes: bc38feddeb ("io: fsync before closing a file channel")
Reviewed-by: "Daniel P. Berrangé" <berrange@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240305195629.9922-1-farosas@suse.de
Link: https://lore.kernel.org/r/20240305174332.2553-1-farosas@suse.de
[peterx: add more comment to the qio_channel_close()]
Signed-off-by: Peter Xu <peterx@redhat.com>
When commit bd2270608f ("migration/ram.c: add a notifier chain for
precopy") added PRECOPY_NOTIFY_SETUP notifiers at the end of
qemu_savevm_state_setup(), it didn't take into account a possible
error in the loop calling vmstate_save() or .save_setup() handlers.
Check ret value before calling the notifiers.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20240304122844.1888308-10-clg@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
This will help detect issues regarding I/O channels usage.
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/20240304122844.1888308-7-clg@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
If a migration stream is broken, the address and flag reading can return
zero. Thus, an irrelevant flag error will be returned instead of EIO.
It can be fixed by additional check after the reading.
Signed-off-by: Maksim Davydov <davydov-max@yandex-team.ru>
Link: https://lore.kernel.org/r/20240304144203.158477-1-davydov-max@yandex-team.ru
Signed-off-by: Peter Xu <peterx@redhat.com>
Commit 90697be889 ("live migration: Serialize vmstate saving in stage
2") introduced device serialization in qemu_savevm_state_iterate(). The
rationale behind it was to first complete migration of slower changing
block devices and only then migrate the RAM, to avoid sending fast
changing RAM pages over and over.
This commit was added a long time ago, and while it was useful back
then, it is not the case anymore:
1. Block migration is deprecated, see commit 66db46ca83 ("migration:
Deprecate block migration").
2. Today there are other iterative devices besides RAM and block, such
as VFIO, which are registered for migration after RAM. With current
serialization behavior, a fast changing device can block other
devices from sending their data, which may prevent migration from
converging in some cases.
The issue described in item 2 was observed in several VFIO migration
scenarios with switchover-ack capability enabled, where some workload on
the VM prevented RAM from ever reaching a hard zero, thus blocking VFIO
initial pre-copy data from being sent. Hence, destination could not ack
switchover and migration could not converge.
Fix that by not serializing iterative devices in
qemu_savevm_state_iterate().
Note that this still doesn't fully prevent device starvation. As
correctly pointed out by Peter [1], a fast changing device might
constantly consume all allocated bandwidth and block the following
devices. However, this scenario is more likely to happen only if
max-bandwidth is low.
[1] https://lore.kernel.org/qemu-devel/Zd6iw9dBhW6wKNxx@x1n/
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240304105339.20713-2-avihaih@nvidia.com
Signed-off-by: Peter Xu <peterx@redhat.com>
- Bryan's fix on multifd compression level API
- Fabiano's mapped-ram series (base + multifd only)
- Steve's amend on cpr document in qapi/
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Merge tag 'migration-next-pull-request' of https://gitlab.com/peterx/qemu into staging
Migartion pull request for 20240304
- Bryan's fix on multifd compression level API
- Fabiano's mapped-ram series (base + multifd only)
- Steve's amend on cpr document in qapi/
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* tag 'migration-next-pull-request' of https://gitlab.com/peterx/qemu: (27 commits)
migration/multifd: Document two places for mapped-ram
tests/qtest/migration: Add a multifd + mapped-ram migration test
migration/multifd: Add mapped-ram support to fd: URI
migration/multifd: Support incoming mapped-ram stream format
migration/multifd: Support outgoing mapped-ram stream format
migration/multifd: Prepare multifd sync for mapped-ram migration
migration/multifd: Add incoming QIOChannelFile support
migration/multifd: Add outgoing QIOChannelFile support
migration/multifd: Add a wrapper for channels_created
migration/multifd: Allow receiving pages without packets
migration/multifd: Allow multifd without packets
migration/multifd: Decouple recv method from pages
migration/multifd: Rename MultiFDSend|RecvParams::data to compress_data
tests/qtest/migration: Add tests for mapped-ram file-based migration
migration/ram: Add incoming 'mapped-ram' migration
migration/ram: Add outgoing 'mapped-ram' migration
migration: Add mapped-ram URI compatibility check
migration/ram: Introduce 'mapped-ram' migration capability
migration/qemu-file: add utility methods for working with seekable channels
io: fsync before closing a file channel
...
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
# Conflicts:
# migration/ram.c
Simplify the exec migration code by using list utility functions.
As a side effect, this also fixes a minor memory leak. On function return,
"g_auto(GStrv) argv" frees argv and each element, which is wrong, because
the function does not own the individual elements. To compensate, the code
uses g_steal_pointer which NULLs argv and prevents the destructor from
running, but argv is leaked.
Fixes: cbab4face5 ("migration: convert exec backend ...")
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Message-ID: <20240227153321.467343-4-armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Add two documentations for mapped-ram migration on two spots that may not
be extremely clear.
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240301091524.39900-1-peterx@redhat.com
Cc: Prasad Pandit <ppandit@redhat.com>
[peterx: fix two English errors per Prasad]
Signed-off-by: Peter Xu <peterx@redhat.com>
If we receive a file descriptor that points to a regular file, there's
nothing stopping us from doing multifd migration with mapped-ram to
that file.
Enable the fd: URI to work with multifd + mapped-ram.
Note that the fds passed into multifd are duplicated because we want
to avoid cross-thread effects when doing cleanup (i.e. close(fd)). The
original fd doesn't need to be duplicated because monitor_get_fd()
transfers ownership to the caller.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/20240229153017.2221-23-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
For the incoming mapped-ram migration we need to read the ramblock
headers, get the pages bitmap and send the host address of each
non-zero page to the multifd channel thread for writing.
Usage on HMP is:
(qemu) migrate_set_capability multifd on
(qemu) migrate_set_capability mapped-ram on
(qemu) migrate_incoming file:migfile
(the ram.h include needs to move because we've been previously relying
on it being included from migration.c. Now file.h will start including
multifd.h before migration.o is processed)
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-22-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
The new mapped-ram stream format uses a file transport and puts ram
pages in the migration file at their respective offsets and can be
done in parallel by using the pwritev system call which takes iovecs
and an offset.
Add support to enabling the new format along with multifd to make use
of the threading and page handling already in place.
This requires multifd to stop sending headers and leaving the stream
format to the mapped-ram code. When it comes time to write the data, we
need to call a version of qio_channel_write that can take an offset.
Usage on HMP is:
(qemu) stop
(qemu) migrate_set_capability multifd on
(qemu) migrate_set_capability mapped-ram on
(qemu) migrate_set_parameter max-bandwidth 0
(qemu) migrate_set_parameter multifd-channels 8
(qemu) migrate file:migfile
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-21-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
The mapped-ram migration can be performed live or non-live, but it is
always asynchronous, i.e. the source machine and the destination
machine are not migrating at the same time. We only need some pieces
of the multifd sync operations.
multifd_send_sync_main()
------------------------
Issued by the ram migration code on the migration thread, causes the
multifd send channels to synchronize with the migration thread and
makes the sending side emit a packet with the MULTIFD_FLUSH flag.
With mapped-ram we want to maintain the sync on the sending side
because that provides ordering between the rounds of dirty pages when
migrating live.
MULTIFD_FLUSH
-------------
On the receiving side, the presence of the MULTIFD_FLUSH flag on a
packet causes the receiving channels to start synchronizing with the
main thread.
We're not using packets with mapped-ram, so there's no MULTIFD_FLUSH
flag and therefore no channel sync on the receiving side.
multifd_recv_sync_main()
------------------------
Issued by the migration thread when the ram migration flag
RAM_SAVE_FLAG_MULTIFD_FLUSH is received, causes the migration thread
on the receiving side to start synchronizing with the recv
channels. Due to compatibility, this is also issued when
RAM_SAVE_FLAG_EOS is received.
For mapped-ram we only need to synchronize the channels at the end of
migration to avoid doing cleanup before the channels have finished
their IO.
Make sure the multifd syncs are only issued at the appropriate times.
Note that due to pre-existing backward compatibility issues, we have
the multifd_flush_after_each_section property that can cause a sync to
happen at EOS. Since the EOS flag is needed on the stream, allow
mapped-ram to just ignore it.
Also emit an error if any other unexpected flags are found on the
stream.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/20240229153017.2221-20-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
On the receiving side we don't need to differentiate between main
channel and threads, so whichever channel is defined first gets to be
the main one. And since there are no packets, use the atomic channel
count to index into the params array.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-19-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
Allow multifd to open file-backed channels. This will be used when
enabling the mapped-ram migration stream format which expects a
seekable transport.
The QIOChannel read and write methods will use the preadv/pwritev
versions which don't update the file offset at each call so we can
reuse the fd without re-opening for every channel.
Contrary to the socket migration, the file migration doesn't need an
asynchronous channel creation process, so expose
multifd_channel_connect() and call it directly.
Note that this is just setup code and multifd cannot yet make use of
the file channels.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/20240229153017.2221-18-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
We'll need to access multifd_send_state->channels_created from outside
multifd.c, so introduce a helper for that.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-17-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
Currently multifd does not need to have knowledge of pages on the
receiving side because all the information needed is within the
packets that come in the stream.
We're about to add support to mapped-ram migration, which cannot use
packets because it expects the ramblock section in the migration file
to contain only the guest pages data.
Add a data structure to transfer pages between the ram migration code
and the multifd receiving threads.
We don't want to reuse MultiFDPages_t for two reasons:
a) multifd threads don't really need to know about the data they're
receiving.
b) the receiving side has to be stopped to load the pages, which means
we can experiment with larger granularities than page size when
transferring data.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-16-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
For the upcoming support to the new 'mapped-ram' migration stream
format, we cannot use multifd packets because each write into the
ramblock section in the migration file is expected to contain only the
guest pages. They are written at their respective offsets relative to
the ramblock section header.
There is no space for the packet information and the expected gains
from the new approach come partly from being able to write the pages
sequentially without extraneous data in between.
The new format also simply doesn't need the packets and all necessary
information can be taken from the standard migration headers with some
(future) changes to multifd code.
Use the presence of the mapped-ram capability to decide whether to
send packets.
This only moves code under multifd_use_packets(), it has no effect for
now as mapped-ram cannot yet be enabled with multifd.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-15-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
Next patches will abstract the type of data being received by the
channels, so do some cleanup now to remove references to pages and
dependency on 'normal_num'.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-14-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
Use a more specific name for the compression data so we can use the
generic for the multifd core code.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-13-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
Add the necessary code to parse the format changes for the
'mapped-ram' capability.
One of the more notable changes in behavior is that in the
'mapped-ram' case ram pages are restored in one go rather than
constantly looping through the migration stream.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-11-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
Implement the outgoing migration side for the 'mapped-ram' capability.
A bitmap is introduced to track which pages have been written in the
migration file. Pages are written at a fixed location for every
ramblock. Zero pages are ignored as they'd be zero in the destination
migration as well.
The migration stream is altered to put the dirty pages for a ramblock
after its header instead of having a sequential stream of pages that
follow the ramblock headers.
Without mapped-ram (current): With mapped-ram (new):
--------------------- --------------------------------
| ramblock 1 header | | ramblock 1 header |
--------------------- --------------------------------
| ramblock 2 header | | ramblock 1 mapped-ram header |
--------------------- --------------------------------
| ... | | padding to next 1MB boundary |
--------------------- | ... |
| ramblock n header | --------------------------------
--------------------- | ramblock 1 pages |
| RAM_SAVE_FLAG_EOS | | ... |
--------------------- --------------------------------
| stream of pages | | ramblock 2 header |
| (iter 1) | --------------------------------
| ... | | ramblock 2 mapped-ram header |
--------------------- --------------------------------
| RAM_SAVE_FLAG_EOS | | padding to next 1MB boundary |
--------------------- | ... |
| stream of pages | --------------------------------
| (iter 2) | | ramblock 2 pages |
| ... | | ... |
--------------------- --------------------------------
| ... | | ... |
--------------------- --------------------------------
| RAM_SAVE_FLAG_EOS |
--------------------------------
| ... |
--------------------------------
where:
- ramblock header: the generic information for a ramblock, such as
idstr, used_len, etc.
- ramblock mapped-ram header: the new information added by this
feature: bitmap of pages written, bitmap size and offset of pages
in the migration file.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-10-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
The mapped-ram migration format needs a channel that supports seeking
to be able to write each page to an arbitrary offset in the migration
stream.
Reviewed-by: "Daniel P. Berrangé" <berrange@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-9-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
Add a new migration capability 'mapped-ram'.
The core of the feature is to ensure that RAM pages are mapped
directly to offsets in the resulting migration file instead of being
streamed at arbitrary points.
The reasons why we'd want such behavior are:
- The resulting file will have a bounded size, since pages which are
dirtied multiple times will always go to a fixed location in the
file, rather than constantly being added to a sequential
stream. This eliminates cases where a VM with, say, 1G of RAM can
result in a migration file that's 10s of GBs, provided that the
workload constantly redirties memory.
- It paves the way to implement O_DIRECT-enabled save/restore of the
migration stream as the pages are ensured to be written at aligned
offsets.
- It allows the usage of multifd so we can write RAM pages to the
migration file in parallel.
For now, enabling the capability has no effect. The next couple of
patches implement the core functionality.
Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-8-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
Add utility methods that will be needed when implementing 'mapped-ram'
migration capability.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: "Daniel P. Berrangé" <berrange@redhat.com>
Link: https://lore.kernel.org/r/20240229153017.2221-7-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
Some minor cleanups and documentation for multifd_recv_sync_main.
Use thread_count as done in other parts of the code. Remove p->id from
the multifd_recv_state sync, since that is global and not tied to a
channel. Add documentation for the sync steps.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-2-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
Some glue code was missing, so that using `qmp_migrate_set_parameters`
to set `multifd-zstd-level` or `multifd-zlib-level` did not work. This
commit adds the glue code to fix that.
Signed-off-by: Bryan Zhang <bryan.zhang@bytedance.com>
Link: https://lore.kernel.org/r/20240301035901.4006936-2-bryan.zhang@bytedance.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Replace with the maximum of the real host page size
and the target page size. This is an exact replacement.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Acked-by: Helge Deller <deller@gmx.de>
Message-Id: <20240102015808.132373-12-richard.henderson@linaro.org>
close_return_path_on_source() retrieves the migration error from the
the QEMUFile '->to_dst_file' to know if a shutdown is required. This
shutdown is required to exit the return-path thread.
Avoid relying on '->to_dst_file' and use migrate_has_error() instead.
(using to_dst_file is a heuristic to infer whether
rp_state.from_dst_file might be stuck on a recvmsg(). Using a generic
method for detecting errors is more reliable. We also want to reduce
dependency on QEMUFile::last_error)
Suggested-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
[added some words about the motivation for this patch]
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240226203122.22894-3-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
The return path thread might hang at a blocking system call. Before
joining the thread we might need to issue a shutdown() on the socket
file descriptor to release it. To determine whether the shutdown() is
necessary we look at the QEMUFile error.
Make sure we only clean up the QEMUFile after the return path has been
waited for.
This fixes a hang when qemu_savevm_state_setup() produced an error
that was detected by migration_detect_error(). That skips
migration_completion() so close_return_path_on_source() would get
stuck waiting for the RP thread to terminate.
Reported-by: Cédric Le Goater <clg@redhat.com>
Tested-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240226203122.22894-2-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
