Re: [Bug 211189] New: vgaarb overrides boot device unexpectedly with Intel and discrete AMDGPU

[cc'd efifb and vgaarb maintainers on bugzilla, but not sure whether
people pay attention to that]

On Thu, Jan 14, 2021 at 10:42:53AM +0000, bugzilla-daemon@bugzilla.kernel.org wrote:

https://bugzilla.kernel.org/show_bug.cgi?id=211189

            Bug ID: 211189
           Summary: vgaarb overrides boot device unexpectedly with Intel
                    and discrete AMDGPU
           Product: Drivers
           Version: 2.5
    Kernel Version: 5.10.7-200.fc33.x86_64
          Hardware: x86-64
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: PCI
          Assignee: drivers_pci@kernel-bugs.osdl.org
          Reporter: dominik@greysector.net
        Regression: No

The system is a MSI Z77A-GD65 mainboard configured to boot in UEFI mode.
Despite setting integrated GPU (from i5-3570K CPU) as the default in firmware
setup, the kernel sets the discrete GPU (Radeon HD 7950) as boot_vga. This
results in wrong order in e.g. switcherooctl:
$ switcherooctl list
Device: 0
  Name:        Advanced Micro Devices, Inc. [AMD®/ATI] Tahiti PRO [Radeon HD
7950/8950 OEM / R9 280]
  Default:     yes
  Environment: DRI_PRIME=pci-0000_01_00_0

Device: 1
  Name:        Intel® HD Graphics 4000
  Default:     no
  Environment: DRI_PRIME=pci-0000_00_02_0
$ lspci -vnn
...
00:02.0 VGA compatible controller [0300]: Intel Corporation Xeon E3-1200 v2/3rd
Gen Core processor Graphics Controller [8086:0162] (rev 09) (prog-if 00 [VGA
controller])
        DeviceName:  Onboard IGD
        Subsystem: Micro-Star International Co., Ltd. [MSI] Device [1462:2111]
        Flags: bus master, fast devsel, latency 0, IRQ 31
        Memory at f7800000 (64-bit, non-prefetchable) [size=4M]
        Memory at d0000000 (64-bit, prefetchable) [size=256M]
        I/O ports at f000 [size=64]
        Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
        Capabilities: [d0] Power Management version 2
        Capabilities: [a4] PCI Advanced Features
        Kernel driver in use: i915
        Kernel modules: i915
...
01:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc.
[AMD/ATI] Tahiti PRO [Radeon HD 7950/8950 OEM / R9 280] [1002:679a] (prog-if 00
[VGA controller])
        Subsystem: Micro-Star International Co., Ltd. [MSI] Device [1462:2761]
        Flags: bus master, fast devsel, latency 0, IRQ 32
        Memory at e0000000 (64-bit, prefetchable) [size=256M]
        Memory at f7d00000 (64-bit, non-prefetchable) [size=256K]
        I/O ports at e000 [size=256]
        Expansion ROM at 000c0000 [disabled] [size=128K]
        Capabilities: [48] Vendor Specific Information: Len=08 <?>
        Capabilities: [50] Power Management version 3
        Capabilities: [58] Express Legacy Endpoint, MSI 00
        Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010
<?>
        Capabilities: [150] Advanced Error Reporting
        Capabilities: [270] Secondary PCI Express
        Capabilities: [2b0] Address Translation Service (ATS)
        Capabilities: [2c0] Page Request Interface (PRI)
        Capabilities: [2d0] Process Address Space ID (PASID)
        Kernel driver in use: amdgpu
        Kernel modules: radeon, amdgpu

$ for f in /sys/bus/pci/devices/*/boot_vga ; do echo -n "$f:" ; cat $f ; done
/sys/bus/pci/devices/0000:00:02.0/boot_vga:0
/sys/bus/pci/devices/0000:01:00.0/boot_vga:1

$ dmesg
...
[    0.267216] pci 0000:01:00.0: BAR 0: assigned to efifb

This is from drivers/video/fbdev/efifb.c and makes me wonder if this
is a firmware defect.  You set 00:02.0 to be the default in firmware
setup, but apparently the EFI FB is using 01:00.0?

[    0.268571] pci 0000:00:02.0: vgaarb: setting as boot VGA device
[    0.268571] pci 0000:00:02.0: vgaarb: VGA device added:
decodes=io+mem,owns=io+mem,locks=none
[    0.268571] pci 0000:01:00.0: vgaarb: VGA device added:
decodes=io+mem,owns=io+mem,locks=none
[    0.268571] pci 0000:00:02.0: vgaarb: no bridge control possible
[    0.268571] pci 0000:01:00.0: vgaarb: bridge control possible
[    0.268571] pci 0000:01:00.0: vgaarb: overriding boot device
[    0.268571] vgaarb: loaded
[    0.754748] efifb: probing for efifb
[    0.754766] efifb: No BGRT, not showing boot graphics
[    0.754768] efifb: framebuffer at 0xe0000000, using 8100k, total 8100k
[    0.754769] efifb: mode is 1920x1080x32, linelength=7680, pages=1
[    0.754770] efifb: scrolling: redraw
[    0.754772] efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0
[    2.984727] i915 0000:00:02.0: vgaarb: changed VGA decodes:
olddecodes=io+mem,decodes=none:owns=io+mem
[    3.011601] [drm] Initialized i915 1.6.0 20200917 for 0000:00:02.0 on minor
0
[    3.213870] [drm] amdgpu kernel modesetting enabled.
[    3.275739] i915 0000:00:02.0: [drm] fb1: i915drmfb frame buffer device
[    3.275972] fb0: switching to amdgpudrmfb from EFI VGA
[    3.276112] amdgpu 0000:01:00.0: vgaarb: deactivate vga console
[    3.276240] [drm] initializing kernel modesetting (TAHITI 0x1002:0x679A
0x1462:0x2761 0x00).
...
[    4.069577] amdgpu 0000:01:00.0: [drm] fb0: amdgpudrmfb frame buffer device
[    4.351324] [drm] Initialized amdgpu 3.40.0 20150101 for 0000:01:00.0 on
minor 1

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