[libvirt PATCH 00/15] RFC: basic CGroup support with qemu:///session

[Daniel P. Berrangé]

On Tue, Apr 07, 2020 at 12:48:26PM +0200, Marc-André Lureau wrote:
> Hi
> 
> On Tue, Apr 7, 2020 at 10:55 AM Pavel Hrdina <phrdina at redhat.com> wrote:
> >
> > On Mon, Apr 06, 2020 at 11:26:57PM +0200, marcandre.lureau at redhat.com wrote:
> > > From: Marc-André Lureau <marcandre.lureau at redhat.com>
> > >
> > > Hi,
> > >
> > > This is a small series that allows basic QEMU VM CGroup support with
> > > the help of machined --user:
> > > https://github.com/systemd/systemd/pull/15312
> > >
> > > The first few patches are fixes to register dbus and slirp-helper
> > > correctly with the VM cgroup.
> > >
> > > A few changes are done to the machined support, adding session
> > > support, and registering the VM to get a systemd scope cgroup under
> > > user machine.slice.
> >
> > Hi,
> >
> > Before we start with anything I would like to know what is the
> > motivation behind having CGroup support for session VMs?
> 
> My initial motivation was to have a way to group VM processes and kill
> them altogether, because I tend to have a lot of them around after a
> while.
> 
> Given that systemd --user is very capable and based on
> https://www.freedesktop.org/wiki/Software/systemd/writing-vm-managers/,
> I thought that was probably the way to go.

Yes, it makes sense. It also should help us close a feature gap
by enabling many of our resource tuning APIs to now work in session
mode, since we can now use cgroups tuning.

> > From the systemd pull request it looks like you would like to have
> > session VMs under the /sys/fs/cgroup/machine.slice which is completely
> > wrong as we should not mix system and session VMs under the same slice.
> 
> No, it is under user.slice, ex with this series:
> 
>    CGroup: /user.slice/user-1000.slice/user at 1000.service
>            ├─machine.slice
>            │ └─machine-qemu\x2delmarco\x2d1\x2dfedora.scope
>            │   ├─24714 /usr/bin/swtpm socket --daemon --ctrl
> type=unixio,path=/run/user/1000/libvirt/qemu/run/swtpm/1-fedora-swtpm.sock,mode=0600
> --tpmstate dir=/home/elmarco/.config/libvirt/qemu/swtpm/053f84e7>
>            │   ├─24716 /usr/bin/dbus-daemon
> --config-file=/run/user/1000/libvirt/qemu/run/dbus/1-fedora-dbus.conf
>            │   ├─24719
> /home/elmarco/src/libslirp-rs/target/debug/libslirp-helper --fd=27
> --dbus-id=slirp-52:54:00:9c:bb:6c
> --dbus-address=unix:path=/run/user/1000/libvirt/qemu/run/dbus/1-fedora-dbus.sock
> --exi>
>            │   ├─24722 /usr/bin/qemu-system-x86_64 -name
> guest=fedora,debug-threads=on -S -object
> secret,id=masterKey0,format=raw,file=/home/elmarco/.config/libvirt/qemu/lib/domain-1-fedora/master-key.aes
> -obje>
>            │   └─emulator

Regards,
Daniel
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