Hi @ajkavanagh, this affects focal-hwe, jammy and will affect any new
releases unless this sysctl is set to 1.
** No longer affects: charm-nova-compute
** Also affects: qemu
Importance: Undecided
Status: New
** No longer affects: qemu
** Also affects: charm-nova-compute
Importance: Undecided
Status: New
--
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https://bugs.launchpad.net/bugs/1926249
Title:
postcopy migration fails in hirsute (solved)
Status in OpenStack Nova Compute Charm:
New
Status in qemu package in Ubuntu:
Invalid
Bug description:
FYI: this is an intended change, can be overwritten via config and
this bug is mostly to have something puzzled users can find via search
engines to explain and solve their issue.
postcopy migration can in some cases be very useful
=> https://wiki.qemu.org/Features/PostCopyLiveMigration
But with Hirsute kernel being 5.11 that now contains the following upstream
change
=>
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d0d4730ac2
Due to that postcopy migration will fail like:
+ lxc exec testkvm-focal-from -- virsh migrate --unsafe --live --postcopy
--postcopy-after-precopy kvmguest-focal-postcopy qemu+ssh://10.85.93.248/system
error: internal error: unable to execute QEMU command
'migrate-set-capabilities': Postcopy is not supported
This will also apply to e.g. a Focal-HWE kernel once on v5.11 or to
Focal userspaces in a container under a Hirsute kernel (that is the
example above).
This was done for security reasons, if you want/need to re-enable un-limited
userfault handling to be able to use postcopy again you'd want/need to set the
control knob to one like:
$ sudo sysctl -w "vm.unprivileged_userfaultfd=1"
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