On Tue, 17 Jun 2025 12:59:10 -0500 Mario Limonciello <superm1@xxxxxxxxxx> wrote: > From: Mario Limonciello <mario.limonciello@xxxxxxx> > > On a mobile system with an AMD integrated GPU + NVIDIA discrete GPU the > AMD GPU is not being selected by some desktop environments for any > rendering tasks. This is because neither GPU is being treated as > "boot_vga" but that is what some environments use to select a GPU [1]. > > The VGA arbiter driver only looks at devices that report as PCI display > VGA class devices. Neither GPU on the system is a PCI display VGA class > device: > > c5:00.0 3D controller: NVIDIA Corporation Device 2db9 (rev a1) > c6:00.0 Display controller: Advanced Micro Devices, Inc. [AMD/ATI] Device 150e (rev d1) > > If the GPUs were looked at the vga_is_firmware_default() function actually > does do a good job at recognizing the case from the device used for the > firmware framebuffer. > > Modify the VGA arbiter code and matching sysfs file entries to examine all > PCI display class devices. The existing logic stays the same. > > This will cause all GPUs to gain a `boot_vga` file, but the correct device > (AMD GPU in this case) will now show `1` and the incorrect device shows `0`. > Userspace then picks the right device as well. > > Link: https://github.com/robherring/libpciaccess/commit/b2838fb61c3542f107014b285cbda097acae1e12 [1] > Suggested-by: Daniel Dadap <ddadap@xxxxxxxxxx> > Acked-by: Thomas Zimmermann <tzimmermann@xxxxxxx> > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx> > --- > drivers/pci/pci-sysfs.c | 2 +- > drivers/pci/vgaarb.c | 8 ++++---- > 2 files changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c > index 268c69daa4d57..c314ee1b3f9ac 100644 > --- a/drivers/pci/pci-sysfs.c > +++ b/drivers/pci/pci-sysfs.c > @@ -1707,7 +1707,7 @@ 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_display(pdev)) > return a->mode; > > return 0; > diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c > index 78748e8d2dbae..63216e5787d73 100644 > --- a/drivers/pci/vgaarb.c > +++ b/drivers/pci/vgaarb.c > @@ -1499,8 +1499,8 @@ 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 PCI display class devices */ > + if (!pci_is_display(pdev)) > return 0; > > /* > @@ -1546,12 +1546,12 @@ 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 all PCI display class 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_display(pdev)) > vga_arbiter_add_pci_device(pdev); > } > At the very least a non-VGA device should not mark that it decodes legacy resources, marking the boot VGA device is only a part of what the VGA arbiter does. It seems none of the actual VGA arbitration interfaces have been considered here though. I still think this is a bad idea and I'm not sure Thomas didn't withdraw his ack in the previous round[1]. Thanks, Alex [1]https://lore.kernel.org/all/bc0a3ac2-c86c-43b8-b83f-edfdfa5ee184@xxxxxxx/
