[systemd-devel] machined: after CPU offline then online, vcpupin KVM guest failed to start

Lennart Poettering lennart at poettering.net
Wed Aug 3 14:56:16 UTC 2016

On Wed, 03.08.16 14:46, Dr. Werner Fink (werner at suse.de) wrote:

> Hi,
> problem with v228 (and I guess this is also later AFAICS from logs of
> current git) that repeating CPU hotplug events (offline/online). The
> root cause is that cpuset.cpus become not restored by machined.
> Please note that libvirt can not do this as it is not allowed to do
> so.

This is a limitation of the kernel cpuset interface, and it's one of
the reasons we do not expose cpusets at all in systemd right
now. Thankfully, there's an alternative to cpusets, which is the CPU
affinity controls exposed via CPUAffinity= in systemd, which do much
of the same, but have less borked semantics.

We'd like to support cpusets directly in systemd, but we don't do this
as long as the kernel interfaces are as borked as they are. For
example, cpusets are flushed out entirely currently when the system
goes through a suspend/resume cycle.

If libvirt has hook-ups with cpuset, then it bypasses systemd for

Either way, this is not a systemd issue at all.

> PS: Using https://github.com/systemd/systemd/issues/new seems to be very limited
> with > *NOTE: Do not submit bug reports about anything but the two most recently
>      > released systemd versions upstream!*

Yes, we do upstream maintainance upstream only. Downstream
maintainance needs to happen downstream.


Lennart Poettering, Red Hat

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