[libvirt PATCH v3] cgroup/LXC: Do not condition availability of v2 by controllers

[Michal Koutný]

Hello.

On Tue, Oct 25, 2022 at 11:33:56AM +0200, Pavel Hrdina <phrdina at redhat.com> wrote:
> Unfortunately this breaks a lot of things and we cannot use it even as
> workaround. Libvirt code has few assumptions as that's how unified mode
> works and when the cgroups v2 backend is enabled for hybrid topology we
> assume that cpuacct, devices controllers are enabled.

To be on the same side -- there's no cpuacct and devices on cgroup v2
(regardless of hybrid or unified mode).

> But in the case of hybrid topology they are enabled by cgroups v1. Due
> to this change we no longer limit access to devices and cpu accounting
> no longer works.

Shouldn't v1 backend still carry that out? (On a higher level -- I
understand that having both backends enabled for the hybrid mode is
what's not working well.)
 
> I'm going to send a patch to revert this one and we need to find yet
> another solution to the issue.

BTW do you have any pointers (a commit) when the hybrid mode could have
become broken for libvirt/lxc? (I estimate from the (lack of) user
reports that it must have worked at the time of libvirt 4.0.)

Thanks,
Michal
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