lxc container startup error and RFC patch

[Jim Fehlig]

On 7/29/21 3:28 PM, Cole Robinson wrote:
> Hi all,
> 
> I'm seeing LXC container startup failures. This is with libvirt git,
> fedora 34 host with systemd-248.6-1.fc34.x86_64 (I didn't confirm with
> other versions). Reproducer:

 From my experience its more related to cgroups. Works with V2-only, doesn't 
work with V1 or hybrid.

> sudo virt-install --connect lxc:/// --name test-container --memory 128
> --boot init=/bin/sh
> 
> Starting install...
> ERROR    error from service:
> GDBus.Error:org.freedesktop.machine1.NoMachineForPID: PID 2145047 does
> not belong to any known machine
> 
> libvirt 7.0.0 works but 7.1.0+ does not. The root error seems to predate
> that, showing up in syslog, but commit 9c1693eff made it fatal:
> 
> commit 9c1693eff427661616ce1bd2795688f87288a412
> Author: Pavel Hrdina <phrdina at redhat.com>
> Date:   Fri Feb 5 16:17:35 2021 +0100
> 
>      vircgroup: use DBus call to systemd for some APIs
> 
> The error comes from virSystemdGetMachineByPID. The PID that shows up in
> the above error message does not match the leader PID as reported by
> machinectl. This change fixes the error but I don't know if it's correct
> or if it has other implications:

I'm not familiar enough with the driver to review your change with confidence.

> diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c
> index 066e013ed4..54ecb1316b 100644
> --- a/src/lxc/lxc_controller.c
> +++ b/src/lxc/lxc_controller.c
> @@ -866,12 +866,12 @@ static int virLXCControllerSetupCgroupLimits(virLXCController *ctrl)
>       nodeset = virDomainNumatuneGetNodeset(ctrl->def->numa, auto_nodeset, -1);
>   
>       if (!(ctrl->cgroup = virLXCCgroupCreate(ctrl->def,
> -                                            ctrl->initpid,
> +                                            getpid(),
>                                               ctrl->nnicindexes,
>                                               ctrl->nicindexes)))
>           goto cleanup;
>   
> -    if (virCgroupAddMachineProcess(ctrl->cgroup, getpid()) < 0)
> +    if (virCgroupAddMachineProcess(ctrl->cgroup, ctrl->initpid) < 0)
>           goto cleanup;
>   
>       /* Add all qemu-nbd tasks to the cgroup */
> 
> 
> Maybe something else isn't working elsewhere. Clearly we try to add both
> pids to the systemd machine, but virSystemdGetMachineByPID is not
> working to match the non-leader pid, which is the one that the LXC
> driver knows about.
> 
> Thoughts?
> Can anyone else reproduce?

https://gitlab.com/libvirt/libvirt/-/issues/182

Regards,
Jim