Re: [PATCH] vfio/igd: Fix incorrect error propagation in vfio_pci_igd_opregion_detect()

[Alex Williamson <alex.williamson@redhat.com>]

On Wed, 21 May 2025 23:40:36 +0800
Tomita Moeko <tomitamoeko@gmail.com> wrote:

> In vfio_pci_igd_opregion_detect(), errp will be set when device does
> not have OpRegion or is hotplugged. This errp will be propergated to

propagated

> pci_qdev_realize(), which interprets it as failure, causing unexpected
> termination on devices without OpRegion like SR-IOV VFs or discrete
> GPUs. Fix it by not setting errp in vfio_pci_igd_opregion_detect().
> 
> This patch also checks if the device has OpRegion before hotplug status
> to prvent unwanted warning messages on non-IGD devices.
> 
> Fixes: c0273e77f2d7 ("vfio/igd: Detect IGD device by OpRegion")
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2968
> Reported-by: Edmund Raile <edmund.raile@protonmail.com>
> Link: https://lore.kernel.org/qemu-devel/30044d14-17ec-46e3-b9c3-63d27a5bde27@gmail.com
> Signed-off-by: Tomita Moeko <tomitamoeko@gmail.com>
> ---
>  hw/vfio/igd.c | 22 ++++++++++------------
>  1 file changed, 10 insertions(+), 12 deletions(-)
> 
> diff --git a/hw/vfio/igd.c b/hw/vfio/igd.c
> index e7952d15a0..e7a9d1ffc1 100644
> --- a/hw/vfio/igd.c
> +++ b/hw/vfio/igd.c
> @@ -187,23 +187,21 @@ static bool vfio_pci_igd_opregion_init(VFIOPCIDevice *vdev,
>  }
>  
>  static bool vfio_pci_igd_opregion_detect(VFIOPCIDevice *vdev,
> -                                         struct vfio_region_info **opregion,
> -                                         Error **errp)
> +                                         struct vfio_region_info **opregion)
>  {
>      int ret;
>  
> -    /* Hotplugging is not supported for opregion access */
> -    if (vdev->pdev.qdev.hotplugged) {
> -        error_setg(errp, "IGD OpRegion is not supported on hotplugged device");
> -        return false;
> -    }
> -
>      ret = vfio_device_get_region_info_type(&vdev->vbasedev,
>                      VFIO_REGION_TYPE_PCI_VENDOR_TYPE | PCI_VENDOR_ID_INTEL,
>                      VFIO_REGION_SUBTYPE_INTEL_IGD_OPREGION, opregion);
>      if (ret) {
> -        error_setg_errno(errp, -ret,
> -                         "Device does not supports IGD OpRegion feature");
> +        return false;
> +    }
> +
> +    /* Hotplugging is not supported for opregion access */
> +    if (vdev->pdev.qdev.hotplugged) {
> +        warn_report("IGD device detected, but OpRegion is not supported "
> +                    "on hotplugged device.");
>          return false;
>      }
>  
> @@ -524,7 +522,7 @@ static bool vfio_pci_igd_config_quirk(VFIOPCIDevice *vdev, Error **errp)
>      }
>  
>      /* IGD device always comes with OpRegion */
> -    if (!vfio_pci_igd_opregion_detect(vdev, &opregion, errp)) {
> +    if (!vfio_pci_igd_opregion_detect(vdev, &opregion)) {
>          return true;
>      }
>      info_report("OpRegion detected on Intel display %x.", vdev->device_id);
> @@ -695,7 +693,7 @@ static bool vfio_pci_kvmgt_config_quirk(VFIOPCIDevice *vdev, Error **errp)
>          return true;
>      }
>  
> -    if (!vfio_pci_igd_opregion_detect(vdev, &opregion, errp)) {
> +    if (!vfio_pci_igd_opregion_detect(vdev, &opregion)) {
>          /* Should never reach here, KVMGT always emulates OpRegion */
>          return false;
>      }