[pve-devel] [PATCH qemu-server] qmeventd: go back to extracting vmid from commandline instead of cgroup file

[Fiona Ebner]

Am 14.06.24 um 11:21 schrieb Fiona Ebner:
> In spirit, this is a revert of 502870a0 ("qmeventd: extract vmid from
> cgroup file instead of cmdline"), but instead of relying on the custom
> 'id' commandline option that's added by a Proxmox VE patch to QEMU,
> rely on the standard 'pidfile' option to extract the VM ID.
> 
> As reported in the community forum [0], at least during stop mode
> backup, it seems to be possible to end up with the VM process having
>> 0::/system.slice/pvescheduler.service
> as its single cgroup entry. It's not clear what exactly happens and
> there was no success to reproduce the issue. Might be a rare bug in
> systemd or in pve-common's enter_systemd_scope() code.
> 
> This was not the first time relying on the cgroup entry caused issues,
> see d0b58753 ("qmeventd: improve getting VMID from PID in presence of
> legacy cgroup entries").
> 
> To avoid such edge cases and issues in the future, go back to
> extracting the VM ID from the process's commandline.
> 
> It's enough to care about the first occurrence of the 'pidfile'
> option, because that's the one added by Proxmox VE, so the 'continue's
> in the loop turn into 'break's. Even though a later option would
> override the first for QEMU itself to use, that's not supported
> anyways and the important part is the VM ID which is present in the
> first.
> 
> [0]: https://forum.proxmox.com/threads/147409/
> 
> Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>

Ping. After it was quiet for ~10 months, there were 2 new reports about
this yesterday:

https://forum.proxmox.com/threads/147409/post-761580