Re: [PATCH v1] hw/s390x/ccw: Mark virtio-pci disable-legacy property as optional

[Cornelia Huck <cohuck@redhat.com>]

On Wed, May 20 2026, Jaehoon Kim <jhkim@linux.ibm.com> wrote:

> The s390-ccw-virtio-11.0 compatibility property for TYPE_VIRTIO_PCI
> "disable-legacy" causes QEMU to abort when instantiating
> vhost-user-fs-pci devices:
>
>   Unexpected error in object_property_find_err() at
>   ../qom/object.c:1284:
>   qemu-system-s390x: -device vhost-user-fs-pci: can't apply
>   global virtio-pci.disable-legacy=off: Property
>   'vhost-user-fs-pci.disable-legacy' not found
>
> The issue occurs because some vhost-user devices like
> vhost-user-fs-pci only implement the non-transitional variant
> and do not define a generic device type. Non-transitional
> devices have disable-legacy hardcoded to "on" and do not
> expose it as a property, while only generic device types have
> the "disable-legacy" property. This affects users running
> older machine versions (11.0 and earlier) even when using the
> latest QEMU version.
>
> Mark the global property as optional so it only applies to
> devices that actually have the property, allowing vhost-user
> devices without a generic variant to be instantiated
> successfully on older machine versions.
>
> Fixes: 26103c13cff0 ("hw/s390x/ccw: Disable legacy virtio-pci by default (v11.1+)")
> Signed-off-by: Jaehoon Kim <jhkim@linux.ibm.com>
> ---
>  hw/s390x/s390-virtio-ccw.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index 4d35f9b10b..25a9fa4955 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -946,7 +946,7 @@ static void ccw_machine_11_0_class_options(MachineClass *mc)
>       * keep legacy virtio-pci enabled.
>       */
>      static GlobalProperty compat[] = {
> -        { TYPE_VIRTIO_PCI, "disable-legacy", "off" },
> +        { TYPE_VIRTIO_PCI, "disable-legacy", "off", .optional = true },
>      };
>      ccw_machine_11_1_class_options(mc);
>      compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat));

Thanks, queued to s390-next.