Re: [PATCH] PCI: vgaarb: Include 0x0380 devices in default selection

[Aaron Ma]

On Mon, Jun 22, 2026 at 1:15 AM Mario Limonciello
<mario.limonciello@xxxxxxx> wrote:
>
>
>
> On 6/18/26 01:18, Aaron Ma wrote:
> > Some firmware boot GPUs report class 0x0380 (PCI_CLASS_DISPLAY_OTHER)
> > instead of PCI_CLASS_DISPLAY_VGA. vgaarb only registers pci_is_vga()
> > devices, so those GPUs are not considered by vga_is_firmware_default().
> >
> > On these systems the AMD GPU matches the EFI framebuffer but is
> > excluded from vgaarb because it is class 0x0380, while the NVIDIA GPU
> > does not match the EFI framebuffer but becomes vga_default_device()
> > through the vgaarb's enabled-device fallback.
> >
> > Register legacy VGA and 0x0380 devices in vgaarb, and expose boot_vga
> > for the same set of devices, so the firmware default device can be
> > selected correctly.
> >
> > Signed-off-by: Aaron Ma <aaron.ma@xxxxxxxxxxxxx>
> > ---
> >   drivers/pci/pci-sysfs.c |  3 ++-
> >   drivers/pci/vgaarb.c    | 10 +++++-----
> >   include/linux/pci.h     | 14 ++++++++++++++
> >   3 files changed, 21 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> > index d37860841260c..843d83ec9550a 100644
> > --- a/drivers/pci/pci-sysfs.c
> > +++ b/drivers/pci/pci-sysfs.c
> > @@ -1717,7 +1717,8 @@ static umode_t pci_dev_attrs_are_visible(struct kobject *kobj,
> >       struct device *dev = kobj_to_dev(kobj);
> >       struct pci_dev *pdev = to_pci_dev(dev);
> >
> > -     if (a == &dev_attr_boot_vga.attr && pci_is_vga(pdev))
> > +     if (a == &dev_attr_boot_vga.attr &&
> > +         pci_is_vga_or_other_display(pdev))
> >               return a->mode;
>  >   >          if (a == &dev_attr_serial_number.attr && pci_get_dsn(pdev))
> > diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
> > index c360eee11dd9e..0e0878189e3d8 100644
> > --- a/drivers/pci/vgaarb.c
> > +++ b/drivers/pci/vgaarb.c
> > @@ -796,7 +796,7 @@ static bool vga_arbiter_add_pci_device(struct pci_dev *pdev)
> >       }
> >
> >       if (vga_is_boot_device(vgadev)) {
> > -             vgaarb_info(&pdev->dev, "setting as boot VGA device%s\n",
> > +             vgaarb_info(&pdev->dev, "setting as boot display device%s\n",
> >                           vga_default_device() ?
> >                           " (overriding previous)" : "");
> >               vga_set_default_device(pdev);
> > @@ -1483,8 +1483,8 @@ static int pci_notify(struct notifier_block *nb, unsigned long action,
> >
> >       vgaarb_dbg(dev, "%s\n", __func__);
> >
> > -     /* Only deal with VGA class devices */
> > -     if (!pci_is_vga(pdev))
> > +     /* Only deal with legacy VGA and other display controller devices */
> > +     if (!pci_is_vga_or_other_display(pdev)) >               return 0;
> >
> >       /*
> > @@ -1530,12 +1530,12 @@ static int __init vga_arb_device_init(void)
> >
> >       bus_register_notifier(&pci_bus_type, &pci_notifier);
> >
> > -     /* Add all VGA class PCI devices by default */
> > +     /* Add legacy VGA and other display controller PCI devices by default */
> >       pdev = NULL;
> >       while ((pdev =
> >               pci_get_subsys(PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID,
> >                              PCI_ANY_ID, pdev)) != NULL) {
> > -             if (pci_is_vga(pdev))
> > +             if (pci_is_vga_or_other_display(pdev))
> >                       vga_arbiter_add_pci_device(pdev);
> >       }
> >
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index 2c4454583c115..195ec1bdac863 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -792,6 +792,20 @@ static inline bool pci_is_vga(struct pci_dev *pdev)
> >       return false;
> >   }
> >
> > +/**
> > + * pci_is_vga_or_other_display - check if the PCI device is VGA or 0x0380
> > + * @pdev: PCI device
> > + *
> > + * Return true for legacy VGA-compatible devices and for "other display
> > + * controller" devices.  Some firmware-selected boot display devices expose
> > + * class 0x0380 instead of PCI_CLASS_DISPLAY_VGA.
> > + */
> > +static inline bool pci_is_vga_or_other_display(struct pci_dev *pdev)
> > +{
> > +     return pci_is_vga(pdev) ||
> > +             (pdev->class >> 8) == PCI_CLASS_DISPLAY_OTHER;
> > +}
> > +
> >   /**
> >    * pci_is_display - check if the PCI device is a display controller
> >    * @pdev: PCI device
>
>
> This patch doesn't seem correct to me.  It's overloading the purpose of
> boot_vga to cover non VGA devices.  We should be using boot_display.
>
> Trying to hypothesize what's going on here - I guess you're seeing
> boot_display set for more than one device due to enumeration order.
>
> Can you see if this helps instead?
>
> ╰─❯ git diff
> diff --git a/arch/x86/video/video-common.c b/arch/x86/video/video-common.c
> index 152789f00fcda..9440eb3a7b15d 100644
> --- a/arch/x86/video/video-common.c
> +++ b/arch/x86/video/video-common.c
> @@ -43,9 +43,6 @@ bool video_is_primary_device(struct device *dev)
>          if (!pci_is_display(pdev))
>                  return false;
>
> -       if (pdev == vga_default_device())
> -               return true;
> -
>   #ifdef CONFIG_SCREEN_INFO
>          numres = screen_info_resources(si, res, ARRAY_SIZE(res));
>          for (i = 0; i < numres; ++i) {

Hi Mario,

I tested your change. boot_display becomes correct, but the issue is not fixed.

The kernel state becomes:

  AMD:    boot_display=1, boot_vga absent
  NVIDIA: boot_display absent, boot_vga=1

Current Xorg checks boot_display || boot_vga, so both GPUs still match.
The selected primary GPU still depends on Xorg's DRM device enumeration order.

So boot_vga is still wrong, and that still matters. The kernel should not
expose boot_vga=1 for NVIDIA when the firmware framebuffer is on AMD.

My patch makes boot_vga and boot_display agree on the AMD boot display.

Thanks,
Aaron