On 16.03.21 17:30, Stefan Reiter wrote: > A "savevm" call (both our async variant and the upstream sync one) use > migration code internally. As such, they both expect migration > capabilities to be set. > > This is usually not a problem, as the default set of capabilities is ok, > however, it leads to differing snapshot settings if one does a snapshot > after a machine has been live-migrated (as the capabilities will persist > from that), which could potentially lead to discrepencies in snapshots > (currently it seems to be fine, but it still makes sense to set them to > safeguard against future changes). > > Note that we do set the "dirty-bitmaps" capability now (if > query-proxmox-support reports true), which has three effects: > > 1) PBS dirty-bitmaps are preserved in snapshots, enabling > fast-incremental backups to work after rollback (as long as no newer > backups exist), including for hibernate/resume > 2) snapshots taken from now on, with a QEMU version supporting bitmap > migration, *might* lead to incompatibility of these snapshots with > QEMU versions that don't know about bitmaps at all (i.e. < 5.0 IIRC?) > - forward compatibility is still given, and all other capabilities we > set go back to very old versions
not an issue, in practice starting a snapshot made with a newer QEMU with and older one did not work often due to the running machine version not being available anyway... > 3) since we now explicitly disable bitmap saving if the version doesn't > report support, we avoid crashes even with not-updated QEMU versions > > Signed-off-by: Stefan Reiter <s.rei...@proxmox.com> > --- > PVE/QemuConfig.pm | 1 + > PVE/QemuServer.pm | 8 ++++++-- > test/snapshot-test.pm | 2 ++ > 3 files changed, 9 insertions(+), 2 deletions(-) > > applied, thanks! Albeit it feels like this could have been two patches and a short comment for the set_migration_caps calls, as they can be slightly unexpected for someone not knowing that half the things QEMU can do base on the migrate code. _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
