Re: [RFC PATCH v3 2/3] libxl: Allow PCI device passthrough using -device Qemu command line

[Daniel P. Berrangé <berrange@xxxxxxxxxx>]

On Tue, Apr 14, 2026 at 08:59:52AM +0000, Teddy Astie wrote:
> Le 10/04/2026 à 17:06, Thierry Escande a écrit :
> > This change makes use of the new option 'hotplug' for host PCI devices
> > passthrough'd to the guest. If hotplug=0 is used in the pci device
> > configuration table, the device will be attached to the guest using the
> > Qemu command line as '-device xen-pci-passthrough,hostaddr=...'
> > 
> > The host device configuration is passed to the -device option as a json
> > array, just like it's done for hotplug using QMP. The json array is
> > created by a new internal function libxl__device_pci_get_qmp_json() that
> > is also used by pci_add_qmp_device_add().
> 
> If (in this specific case) we're not using QMP anymore, I think 
> libxl__device_pci_get_qmp_json should lose the "qmp" qualification.
> (unless QEMU also considers JSON-formatted command-line paramters as QMP)

FWIW, from the QEMU POV, 'QMP' refers to the monitor protocol,
whose specification is defined using the 'QAPI' schema language.

QEMU is increasing enabling use of JSON on the command line, by
having the CLI args parsed using 'QAPI' visitors. In these cases,
the 'QAPI' data structures are shared between the command line
and QMP in most cases.

IOW, in this case, perhaps "qapi_json" is a more accurate name
than 'qmp_json' if libxl is returning a JSON doc that represents
an object defined using QAPI.


With regards,
Daniel
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