[XEN PATCH] libxl: Fix device_add QMP calls with QEMU 9.2 and newer

[XEN PATCH] libxl: Fix device_add QMP calls with QEMU 9.2 and newer

[Anthony PERARD]

From: Anthony PERARD <anthony.perard@vates.tech>

QEMU used to ignore JSON types and do conversion string <-> integer
automatically for the command "device_add", but that was removed in
QEMU 9.2 (428d1789df91 ("docs/about: Belatedly document tightening of
QMP device_add checking")).

Fixes: 9718ab394d5d ("libxl_usb: Make libxl__device_usbctrl_add uses ev_qmp")
Fixes: 40c7eca10a82 ("libxl_usb: Make libxl__device_usbdev_add uses ev_qmp")
Signed-off-by: Anthony PERARD <anthony.perard@vates.tech>
---

Notes:
    I've check other `device_add` call site which are for PCI devices and
    CPUs, and they both are already correct.

 tools/libs/light/libxl_usb.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/tools/libs/light/libxl_usb.c b/tools/libs/light/libxl_usb.c
index c5ae59681c..4e7c409fe6 100644
--- a/tools/libs/light/libxl_usb.c
+++ b/tools/libs/light/libxl_usb.c
@@ -367,10 +367,10 @@ static int libxl__device_usbctrl_add_hvm(libxl__egc *egc, libxl__ev_qmp *qmp,
     case 3:
         libxl__qmp_param_add_string(gc, &qmp_args,
                                     "driver", "nec-usb-xhci");
-        libxl__qmp_param_add_string(gc, &qmp_args, "p2",
-                                    GCSPRINTF("%d", usbctrl->ports));
-        libxl__qmp_param_add_string(gc, &qmp_args, "p3",
-                                    GCSPRINTF("%d", usbctrl->ports));
+        libxl__qmp_param_add_integer(gc, &qmp_args, "p2",
+                                     usbctrl->ports);
+        libxl__qmp_param_add_integer(gc, &qmp_args, "p3",
+                                     usbctrl->ports);
         break;
     default:
         abort(); /* Should not be possible. */
@@ -411,10 +411,10 @@ static int libxl__device_usbdev_add_hvm(libxl__egc *egc, libxl__ev_qmp *qmp,
         GCSPRINTF("xenusb-%d.0", usbdev->ctrl));
     libxl__qmp_param_add_string(gc, &qmp_args, "port",
         GCSPRINTF("%d", usbdev->port));
-    libxl__qmp_param_add_string(gc, &qmp_args, "hostbus",
-        GCSPRINTF("%d", usbdev->u.hostdev.hostbus));
-    libxl__qmp_param_add_string(gc, &qmp_args, "hostaddr",
-        GCSPRINTF("%d", usbdev->u.hostdev.hostaddr));
+    libxl__qmp_param_add_integer(gc, &qmp_args, "hostbus",
+                                 usbdev->u.hostdev.hostbus);
+    libxl__qmp_param_add_integer(gc, &qmp_args, "hostaddr",
+                                 usbdev->u.hostdev.hostaddr);
 
     return libxl__ev_qmp_send(egc, qmp, "device_add", qmp_args);
 }
-- 
Anthony PERARD

Re: [XEN PATCH] libxl: Fix device_add QMP calls with QEMU 9.2 and newer

[Juergen Gross]

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On 15.12.25 14:51, Anthony PERARD wrote:
> From: Anthony PERARD <anthony.perard@vates.tech>
> 
> QEMU used to ignore JSON types and do conversion string <-> integer
> automatically for the command "device_add", but that was removed in
> QEMU 9.2 (428d1789df91 ("docs/about: Belatedly document tightening of
> QMP device_add checking")).
> 
> Fixes: 9718ab394d5d ("libxl_usb: Make libxl__device_usbctrl_add uses ev_qmp")
> Fixes: 40c7eca10a82 ("libxl_usb: Make libxl__device_usbdev_add uses ev_qmp")
> Signed-off-by: Anthony PERARD <anthony.perard@vates.tech>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

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Re: [XEN PATCH] libxl: Fix device_add QMP calls with QEMU 9.2 and newer

[Jan Beulich]

On 15.12.2025 14:51, Anthony PERARD wrote:
> From: Anthony PERARD <anthony.perard@vates.tech>
> 
> QEMU used to ignore JSON types and do conversion string <-> integer
> automatically for the command "device_add", but that was removed in
> QEMU 9.2 (428d1789df91 ("docs/about: Belatedly document tightening of
> QMP device_add checking")).

And older qemu accepts integers as well?

Jan

Re: [XEN PATCH] libxl: Fix device_add QMP calls with QEMU 9.2 and newer

[Anthony PERARD]

On Mon, Dec 15, 2025 at 03:11:53PM +0100, Jan Beulich wrote:
> On 15.12.2025 14:51, Anthony PERARD wrote:
> > From: Anthony PERARD <anthony.perard@vates.tech>
> > 
> > QEMU used to ignore JSON types and do conversion string <-> integer
> > automatically for the command "device_add", but that was removed in
> > QEMU 9.2 (428d1789df91 ("docs/about: Belatedly document tightening of
> > QMP device_add checking")).
> 
> And older qemu accepts integers as well?

As the QEMU document explains about the removed feature is that they
should. We already have two users of `device_add` which use integers for
some arguments. And just to be sure, I've just tested with QEMU 8.0, the
patch works fine.

Cheers,

-- 
Anthony PERARD

Re: [XEN PATCH] libxl: Fix device_add QMP calls with QEMU 9.2 and newer

[Maximilian Engelhardt]

On Monday, 15 December 2025 15:41:02 CET Anthony PERARD wrote:
> On Mon, Dec 15, 2025 at 03:11:53PM +0100, Jan Beulich wrote:
> > On 15.12.2025 14:51, Anthony PERARD wrote:
> > > From: Anthony PERARD <anthony.perard@vates.tech>
> > > 
> > > QEMU used to ignore JSON types and do conversion string <-> integer
> > > automatically for the command "device_add", but that was removed in
> > > QEMU 9.2 (428d1789df91 ("docs/about: Belatedly document tightening of
> > > QMP device_add checking")).
> > 
> > And older qemu accepts integers as well?
> 
> As the QEMU document explains about the removed feature is that they
> should. We already have two users of `device_add` which use integers for
> some arguments. And just to be sure, I've just tested with QEMU 8.0, the
> patch works fine.
> 
> Cheers,

Can this patch be picked for the stable branches? I'm in particular interested 
in 4.20 which is in Debian stable.

Thanks,
Maxi

Re: [XEN PATCH] libxl: Fix device_add QMP calls with QEMU 9.2 and newer

[Anthony PERARD]

On Thu, Feb 19, 2026 at 02:29:07PM +0100, Maximilian Engelhardt wrote:
> On Monday, 15 December 2025 15:41:02 CET Anthony PERARD wrote:
> > On Mon, Dec 15, 2025 at 03:11:53PM +0100, Jan Beulich wrote:
> > > On 15.12.2025 14:51, Anthony PERARD wrote:
> > > > From: Anthony PERARD <anthony.perard@vates.tech>
> > > > 
> > > > QEMU used to ignore JSON types and do conversion string <-> integer
> > > > automatically for the command "device_add", but that was removed in
> > > > QEMU 9.2 (428d1789df91 ("docs/about: Belatedly document tightening of
> > > > QMP device_add checking")).
> > > 
> > > And older qemu accepts integers as well?
> > 
> > As the QEMU document explains about the removed feature is that they
> > should. We already have two users of `device_add` which use integers for
> > some arguments. And just to be sure, I've just tested with QEMU 8.0, the
> > patch works fine.
> > 
> > Cheers,
> 
> Can this patch be picked for the stable branches? I'm in particular interested 
> in 4.20 which is in Debian stable.

Done, thanks.


--
Anthony Perard | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech

Re: [XEN PATCH] libxl: Fix device_add QMP calls with QEMU 9.2 and newer

[Maximilian Engelhardt]

On Monday, 9 March 2026 15:48:55 CET Anthony PERARD wrote:
> On Thu, Feb 19, 2026 at 02:29:07PM +0100, Maximilian Engelhardt wrote:
[...]
> > Can this patch be picked for the stable branches? I'm in particular
> > interested in 4.20 which is in Debian stable.
> 
> Done, thanks.

Thanks also.

We meanwhile got two reports in Debian from people running into that issue 
(plus me), so it's good to see it fixed.

We will pull the fix with the next xen update in Debian (but not yet the 
upcoming 13.4 point release), which we always base on the upstream stable 
branch.

Maxi

Re: [XEN PATCH] libxl: Fix device_add QMP calls with QEMU 9.2 and newer

[Maximilian Engelhardt]

On Monday, 15 December 2025 14:51:24 CET Anthony PERARD wrote:
> From: Anthony PERARD <anthony.perard@vates.tech>
> 
> QEMU used to ignore JSON types and do conversion string <-> integer
> automatically for the command "device_add", but that was removed in
> QEMU 9.2 (428d1789df91 ("docs/about: Belatedly document tightening of
> QMP device_add checking")).
> 
> Fixes: 9718ab394d5d ("libxl_usb: Make libxl__device_usbctrl_add uses
> ev_qmp")
> Fixes: 40c7eca10a82 ("libxl_usb: Make libxl__device_usbdev_add
> uses ev_qmp")
> Signed-off-by: Anthony PERARD <anthony.perard@vates.tech>

I can confirm with this patch usb passthrough works on the debian xen 4.20 
package.

Tested-by: Maximilian Engelhardt <maxi@daemonizer.de>