Crashes under Xen with Radeon graphics card

Fri Dec 15 11:56:39 UTC 2023

Hi,

I recently stumbled over a test system which showed crashes probably resulting
from memory being overwritten randomly.

The problem is occurring only in Dom0 when running under Xen. It seems to be
present since at least kernel 6.3 (I didn't go back further yet), and it seems
NOT to be present in kernel 5.14.

I tracked the problem down to the initialization of the graphics card (the
problem might surface only later, but at least an early initialization
failure made the problem go away).

# lspci
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Caicos 
XTX [Radeon HD 8490 / R5 235X OEM]
01:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Caicos HDMI Audio 
[Radeon HD 6450 / 7450/8450/8490 OEM / R5 230/235/235X OEM]

I had a working .config and one which did produce the crashes, so I narrowed
the problem down to detect that the important difference was in the area of
firmware loading (the working .config didn't have CONFIG_FW_LOADER_COMPRESS_XZ
set, causing firmware loading for the card to fail). This was of course not
the real problem, but it caused the card initialization to fail.

I manually decompressed the firmware files one by one to see whether the
problem would be in the decompressor or probably in the driver of the card.

The last step without crash was:

# dmesg | grep radeon
[   10.106405] [drm] radeon kernel modesetting enabled.
[   10.106455] radeon 0000:01:00.0: vgaarb: deactivate vga console
[   10.222944] radeon 0000:01:00.0: VRAM: 1024M 0x0000000000000000 - 
0x000000003FFFFFFF (1024M used)
[   10.252921] radeon 0000:01:00.0: GTT: 1024M 0x0000000040000000 - 
0x000000007FFFFFFF
[   10.278255] [drm] radeon: 1024M of VRAM memory ready
[   10.295828] [drm] radeon: 1024M of GTT memory ready.
[   10.295867] radeon 0000:01:00.0: Direct firmware load for 
radeon/CAICOS_pfp.bin succeeded
[   10.330846] radeon 0000:01:00.0: Direct firmware load for 
radeon/CAICOS_me.bin succeeded
[   10.330858] radeon 0000:01:00.0: Direct firmware load for radeon/BTC_rlc.bin 
succeeded
[   10.330870] radeon 0000:01:00.0: Direct firmware load for 
radeon/CAICOS_mc.bin failed with error -2
[   10.380979] ni_cp: Failed to load firmware "radeon/CAICOS_mc.bin"
[   10.381006] [drm:evergreen_init [radeon]] *ERROR* Failed to load firmware!
[   10.405765] radeon 0000:01:00.0: Fatal error during GPU init
[   10.432107] [drm] radeon: finishing device.
[   10.439179] [drm] radeon: ttm finalized
[   10.463203] radeon: probe of 0000:01:00.0 failed with error -2

And with decompressing radeon/CAICOS_mc.bin I got:

# dmesg | grep radeon
[   10.266491] [drm] radeon kernel modesetting enabled.
[   10.266552] radeon 0000:01:00.0: vgaarb: deactivate vga console
[   10.456047] radeon 0000:01:00.0: VRAM: 1024M 0x0000000000000000 - 
0x000000003FFFFFFF (1024M used)
[   10.470270] radeon 0000:01:00.0: GTT: 1024M 0x0000000040000000 - 
0x000000007FFFFFFF
[   10.566946] [drm] radeon: 1024M of VRAM memory ready
[   10.576891] [drm] radeon: 1024M of GTT memory ready.
[   10.586971] radeon 0000:01:00.0: Direct firmware load for 
radeon/CAICOS_pfp.bin succeeded
[   10.611886] radeon 0000:01:00.0: Direct firmware load for 
radeon/CAICOS_me.bin succeeded
[   10.611909] radeon 0000:01:00.0: Direct firmware load for radeon/BTC_rlc.bin 
succeeded
[   10.611938] radeon 0000:01:00.0: Direct firmware load for 
radeon/CAICOS_mc.bin succeeded
[   10.660599] radeon 0000:01:00.0: Direct firmware load for 
radeon/CAICOS_smc.bin failed with error -2
[   10.660601] smc: error loading firmware "radeon/CAICOS_smc.bin"
[   10.661676] [drm] radeon: power management initialized
[   10.713666] radeon 0000:01:00.0: Direct firmware load for radeon/SUMO_uvd.bin 
failed with error -2
[   10.713668] radeon 0000:01:00.0: radeon_uvd: Can't load firmware 
"radeon/SUMO_uvd.bin"
[   10.713669] radeon 0000:01:00.0: failed UVD (-2) init.
[   10.714787] [drm] enabling PCIE gen 2 link speeds, disable with 
radeon.pcie_gen2=0
[   10.809213] radeon 0000:01:00.0: WB enabled
[   10.817528] radeon 0000:01:00.0: fence driver on ring 0 use gpu addr 
0x0000000040000c00
[   10.833755] radeon 0000:01:00.0: fence driver on ring 3 use gpu addr 
0x0000000040000c0c
[   10.850330] radeon 0000:01:00.0: radeon: MSI limited to 32-bit
[   10.862154] radeon 0000:01:00.0: radeon: using MSI.
[   10.871930] [drm] radeon: irq initialized.
[   11.062028] [drm] Initialized radeon 2.50.0 20080528 for 0000:01:00.0 on minor 0
[   11.119723] [drm:radeon_dvi_detect [radeon]] *ERROR* DVI-I-1: probed a 
monitor but no|invalid EDID
[   11.411370] fbcon: radeondrmfb (fb0) is primary device
[   11.507252] radeon 0000:01:00.0: [drm] fb0: radeondrmfb frame buffer device
[   11.674028] [drm:radeon_dvi_detect [radeon]] *ERROR* DVI-I-1: probed a 
monitor but no|invalid EDID
[   11.834317] [drm:radeon_dvi_detect [radeon]] *ERROR* DVI-I-1: probed a 
monitor but no|invalid EDID
[   28.313041] snd_hda_intel 0000:01:00.1: bound 0000:01:00.0 (ops 
radeon_audio_component_bind_ops [radeon])
[   44.371991] [drm:radeon_dvi_detect [radeon]] *ERROR* DVI-I-1: probed a 
monitor but no|invalid EDID
[   44.428068] [drm:radeon_dvi_detect [radeon]] *ERROR* DVI-I-1: probed a 
monitor but no|invalid EDID

followed by a crash some seconds after the system was up.

The crashes vary, but often the kernel accesses non-canonical addresses or
tries to map illegal physical addresses. Sometimes the system is just
hanging, either with softlockups or without any further signs of being
alive.

I can easily reproduce the problem, so any debug patches to narrow down the
problem are welcome.

Juergen
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