Thanks for confirming Marcel. Now we understand that -readconfig isn't
going away we can continue to preallocate the pcie-root-ports via the
config file as you suggest.

Thanks
Tom

On Tue, 18 May 2021 at 15:39, Marcel Apfelbaum <mapfelba@redhat.com> wrote:

> Hi Thomas,
>
>
> On Tue, May 18, 2021 at 3:29 PM Thomas Parrott
> <thomas.parrott@canonical.com> wrote:
> >
> > Due to QEMU moving towards a QMP configuration mechanism and away from
> config file support, the LXD team are currently in the process of migrating
> to using QMP to add devices to VMs (so that we can support the use of QEMU
> 6.0).
> >
> > Currently we are using the `-S` flag to freeze CPU at startup, then
> using QMP to add NIC devices via the `device_add` command, and then using
> the `cont` command to start the VM guest.
> >
> > However we have found that it is apparently not possible to add a
> pcie-root-port device via QMP.
> >
> > Initially we tried using something like:
> >
> > device_add
> {"id":"qemu_pcie5","driver":"pcie-root-port","bus":"pcie.0","addr":"1.5","chassis":5,"multifunction":"on"}
> >
> > Which was a straight conversion from the current config file we use.
> >
> > However this gave the error:
> >
> > Error: Bus 'pcie.0' does not support hotplugging
> >
> > Then I found the `--preconfig` flag which sounded interesting, so we
> removed the use of `-daemonize` which prevents the use of --preconfig` and
> then tried adding the pcie-root-port devices in the preconfig stage.
> >
> > But this resulted in the error:
> >
> > The command 'device_add' isn't permitted in 'preconfig' state
> >
> > So we wondered is this a bug, or if not, what is the correct way to be
> adding pcie-root-ports going forward?
>
> The pcie-root-ports cannot be hot-plugged, you will need to
> pre-allocate enough pcie-root-ports for your needs.
> PCI(e) devices can be hot-plugged into the pre-allocated pcie-root-ports.
>
> Thanks,
> Marcel
>
> >
> > Thanks
> > Tom Parrott
> >
> >
>
>