[SRU] [H/Unstable/OEM-5.10] [PATCH 0/1] Select correct boot VGA when BIOS doesn't do it properly

[Kai-Heng Feng]

BugLink: https://bugs.launchpad.net/bugs/1929217

[Impact]
On HP EliteDesk 805 G7 desktop, when a add-in discrete GFX card is
present but the display is connected to integrated GPU, BIOS cannot find
the correct boot VGA. Hence, wrong OpenGL/Vulkan library is used, makes
the desktop environment very laggy.

[Fix]
The current heuristic picks the fallback VGA device with lowest PCI
device number. Based on the current heuristic, also check for ACPI video
device which should be the integrated VGA device.

[Test]
Check if the integrated GPU is the boot VGA:
$ cat /sys/bus/pci/devices/0000\:08\:00.0/boot_vga 
0

After applying the patch:
$ cat /sys/bus/pci/devices/0000\:08\:00.0/boot_vga 
1

[Where problems could occur]
When there are multiple GPUs that are ACPI video devices, and BIOS
failed to find a VGA to POST, the new heuristic introduces new behavior.

Since multiple ACPI video devices are on laptops, the EFI base should
already be correct otherwise there's no POST. If that really happens the
laptop is completely broken at first place.

Kai-Heng Feng (1):
  vgaarb: Use ACPI HID name to find integrated GPU

 drivers/gpu/vga/vgaarb.c | 31 ++++++++++++++++++++++++++-----
 1 file changed, 26 insertions(+), 5 deletions(-)

-- 
2.31.1