Public bug reported: 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" ** Affects: qemu (Ubuntu) Importance: Undecided Status: Invalid ** Changed in: qemu (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1926249 Title: postcopy migration fails in hirsute (solved) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1926249/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
