Message ID | 20210204124834.774401-1-berrange@redhat.com (mailing list archive) |
---|---|
Headers | show |
Series | migration: bring improved savevm/loadvm/delvm to QMP | expand |
* Daniel P. Berrangé (berrange@redhat.com) wrote: > v1: https://lists.gnu.org/archive/html/qemu-devel/2020-07/msg00866.html > v2: https://lists.gnu.org/archive/html/qemu-devel/2020-07/msg07523.html > v3: https://lists.gnu.org/archive/html/qemu-devel/2020-08/msg07076.html > v4: https://lists.gnu.org/archive/html/qemu-devel/2020-09/msg05221.html > v5: https://lists.gnu.org/archive/html/qemu-devel/2020-10/msg00587.html > v6: https://lists.gnu.org/archive/html/qemu-devel/2020-10/msg02158.html > v7: https://lists.gnu.org/archive/html/qemu-devel/2020-10/msg06205.html > v8: https://lists.gnu.org/archive/html/qemu-devel/2020-11/msg06464.html > v9: https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg05016.html > vA: https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg00620.html > > This series aims to provide a better designed replacement for the > savevm/loadvm/delvm HMP commands, which despite their flaws continue > to be actively used in the QMP world via the HMP command passthrough > facility. Queued. > The main problems addressed are: > > - The logic to pick which disk to store the vmstate in is not > satsifactory. > > The first block driver state cannot be assumed to be the root disk > image, it might be OVMF varstore and we don't want to store vmstate > in there. > > - The logic to decide which disks must be snapshotted is hardwired > to all disks which are writable > > Again with OVMF there might be a writable varstore, but this can be > raw rather than qcow2 format, and thus unable to be snapshotted. > While users might wish to snapshot their varstore, in some/many/most > cases it is entirely uneccessary. Users are blocked from snapshotting > their VM though due to this varstore. > > - The commands are synchronous blocking execution and returning > errors immediately. > > This is partially addressed by integrating with the job framework. > This forces the client to use the async commands to determine > the completion status or error message from the operations. > > In the block code I've only dealt with node names for block devices, as > IIUC, this is all that libvirt should need in the -blockdev world it now > lives in. IOW, I've made not attempt to cope with people wanting to use > these QMP commands in combination with -drive args, as libvirt will > never use -drive with a QEMU new enough to have these new commands. > > The main limitations of this current impl > > - The snapshot process runs serialized in the main thread. ie QEMU > guest execution is blocked for the duration. The job framework > lets us fix this in future without changing the QMP semantics > exposed to the apps. > > - Most vmstate loading errors just go to stderr, as they are not > using Error **errp reporting. Thus the job framework just > reports a fairly generic message > > "Error -22 while loading VM state" > > Again this can be fixed later without changing the QMP semantics > exposed to apps. > > I've done some minimal work in libvirt to start to make use of the new > commands to validate their functionality, but this isn't finished yet. > > My ultimate goal is to make the GNOME Boxes maintainer happy again by > having internal snapshots work with OVMF: > > https://gitlab.gnome.org/GNOME/gnome-boxes/-/commit/c486da262f6566326fbcb5e= > f45c5f64048f16a6e > > Changed in v11: > > - Add missing docs for events for snapshot-delete > - Fix mistaken operation name in snapshot-delete docs > > Changed in v10: > > - Fix some mis-placed patch chunks > - Update qapi version number annotations > - Move iotests to new naming scheme > - Fix shell based iotests in tests/qemu-iotests/tests subdir > - Expand QAPI examples > - Remove bogus submodule commit update > - Optimize shell pattern matching code > - Misc other typo/whitespace fixes > > Changed in v9: > > - Rebase to git master to resolve conflicts > - Fixed accidental regression in error handling in previous v8 > - Fixed formatting of iotest expected output now that we switched > to preserving whitespace in QMP input > > Changed in v8: > > - Rebase to git master to resolve conflicts > - Updated QAPI since versions to 6.0 > > Changed in v7: > > - Incorporate changes from: > > https://lists.gnu.org/archive/html/qemu-devel/2020-10/msg03165.html > > - Tweaked error message > > Changed in v6: > > - Resolve many conflicts with recent replay changes > - Misc typos in QAPI > > Changed in v5: > > - Fix prevention of tag overwriting > - Refactor and expand test suite coverage to validate > more negative scenarios > > Changed in v4: > > - Make the device lists mandatory, dropping all support for > QEMU's built-in heuristics to select devices. > > - Improve some error reporting and I/O test coverage > > Changed in v3: > > - Schedule a bottom half to escape from coroutine context in > the jobs. This is needed because the locking in the snapshot > code goes horribly wrong when run from a background coroutine > instead of the main event thread. > > - Re-factor way we iterate over devices, so that we correctly > report non-existant devices passed by the user over QMP. > > - Add QAPI docs notes about limitations wrt vmstate error > reporting (it all goes to stderr not an Error **errp) > so QMP only gets a fairly generic error message currently. > > - Add I/O test to validate many usage scenarios / errors > > - Add I/O test helpers to handle QMP events with a deterministic > ordering > > - Ensure 'delete-snapshot' reports an error if requesting > delete from devices that don't support snapshot, instead of > silently succeeding with no erro. > > Changed in v2: > > - Use new command names "snapshot-{load,save,delete}" to make it > clear that these are different from the "savevm|loadvm|delvm" > as they use the Job framework > > - Use an include list for block devs, not an exclude list > > Daniel P. Berrang=C3=A9 (11): > block: push error reporting into bdrv_all_*_snapshot functions > migration: stop returning errno from load_snapshot() > block: add ability to specify list of blockdevs during snapshot > block: allow specifying name of block device for vmstate storage > block: rename and alter bdrv_all_find_snapshot semantics > migration: control whether snapshots are ovewritten > migration: wire up support for snapshot device selection > migration: introduce a delete_snapshot wrapper > iotests: add support for capturing and matching QMP events > iotests: fix loading of common.config from tests/ subdir > migration: introduce snapshot-{save,load,delete} QMP commands > > Philippe Mathieu-Daud=C3=A9 (1): > migration: Make save_snapshot() return bool, not 0/-1 > > block/monitor/block-hmp-cmds.c | 7 +- > block/snapshot.c | 256 ++++++--- > include/block/snapshot.h | 23 +- > include/migration/snapshot.h | 47 +- > migration/savevm.c | 296 ++++++++-- > monitor/hmp-cmds.c | 12 +- > qapi/job.json | 9 +- > qapi/migration.json | 173 ++++++ > replay/replay-debugging.c | 12 +- > replay/replay-snapshot.c | 5 +- > softmmu/vl.c | 2 +- > tests/qemu-iotests/267.out | 12 +- > tests/qemu-iotests/common.qemu | 106 +++- > tests/qemu-iotests/common.rc | 10 +- > .../tests/internal-snapshots-qapi | 386 +++++++++++++ > .../tests/internal-snapshots-qapi.out | 520 ++++++++++++++++++ > 16 files changed, 1721 insertions(+), 155 deletions(-) > create mode 100755 tests/qemu-iotests/tests/internal-snapshots-qapi > create mode 100644 tests/qemu-iotests/tests/internal-snapshots-qapi.out > > --=20 > 2.29.2 > > >