Re: Adding pcie-root-port devices via QMP apparently isn't possible

[Thomas Parrott <thomas.parrott@canonical.com>]

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I meant to also add that it has been suggested we could discuss this
further on one of the forthcoming weekly community calls.

Thanks
Tom

On Tue, 18 May 2021 at 13:28, 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?
>
> Thanks
> Tom Parrott
>
>
>

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