libvirt/src/qemu/postcopy-migration.sysctl

# This is needed to support post-copy migration for QEMU run by libvirt,
# i.e., unprivileged, as userfaultfd is by default only available to
# privileged processes.
# It can be safely overridden by a file in /etc/sysctl.d/ in case post-copy
# migration is not used on the host.
-vm.unprivileged_userfaultfd = 1
qemu: Enable unprivileged userfaultfd for post-copy migration Userfaultfd is by default allowed only for privileged processes. Since libvirt runs QEMU unprivileged, we need to enable unprivileged access to userfaultfd to enable post-copy migration. https://bugzilla.redhat.com/show_bug.cgi?id=1945420 Signed-off-by: Jiri Denemark <jdenemar@redhat.com> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> 2021-12-02 14:43:27 +00:00			`# This is needed to support post-copy migration for QEMU run by libvirt,`
			`# i.e., unprivileged, as userfaultfd is by default only available to`
			`# privileged processes.`
			`# It can be safely overridden by a file in /etc/sysctl.d/ in case post-copy`
			`# migration is not used on the host.`
qemu: Ignore missing vm.unprivileged_userfaultfd sysctl Older kernels did not support this sysctl, but they did not restrict userfaultfd in any way so everything worked as if vm.unprivileged_userfaultfd was set to 1. Thus we can safely ignore errors when setting the value. Signed-off-by: Jiri Denemark <jdenemar@redhat.com> Reviewed-by: Ján Tomko <jtomko@redhat.com> 2022-02-09 10:08:42 +00:00			`-vm.unprivileged_userfaultfd = 1`