[PATCH v2] iommu/amd: Force identity mode for selected GPUs only

[Arthur Marsh <arthur.marsh@internode.on.net>]

On a system using an APU (no discrete graphics card):

model name      : AMD A10-6800K APU with Radeon(tm) HD Graphics
stepping        : 1
microcode       : 0x6001119

I was getting the following, git-bisected back to:

commit bf5bdfd1f8d4ad5c6020468d09b68b09c2adc5c2 (HEAD)
Author: Vasant Hegde <vasant.hegde@amd.com>
Date:   Mon Aug 24 08:58:21 2026 +0000

    iommu/amd: Force identity mode for selected GPUs only

I could only photograph and OCR the screen, so not a lot of data could be 
captured:

1.295232] </TASK>

1.295233] Modules linked in:

1.295237] CR2: 000000000000003c

1.295242] ---[ end trace 0000000000000000 1---

1.295245] RIP: 0010:amd_iommu_def_domain_type+0x76/0xb0

1.295250] Code: ff 25 00 7f ff ff 3d 00 00 03 00 75 cb 83 02 01 75 3f 48 81

ef do 00 00 00 48 8b 57 10 48 8b 42 10 48 85 со 74 04 48 8b 42 38 <66> 81 78 3c

32 10 74 a6 55 31 ff 48 89 e5 e8 d7 ee 3c 00 5d 83 fo

1.295253] RSP: 0018: ffffc90000027c20 EFLACS: 00010246

1.295256] RAX: 000000 RBX: ffff888100f0d5c0

RCX: 00000000ffffffff

1.295258] RDX: ffff888100dd8000 RSI: ffffffff82437607

RDI: ffff888100fc7000

1.295260) RBP: ffffc90000027c60 R08: 0000000000000001

R09: 0000000000000000

1.295262] R10: 0000000003 R11: 0000000000000001

R12: ffff888100fc70d0

1.295264] R13: 0000000000000000 R14: ffff888100aedc48

R15: 0000000000000000

1.295266] FS: 000000000000(0000) CS:ffff8884acefe000(0000) knICS: 00000

3000000000

1.295269] CS: 0010 DS: 0000 ES: 0000 CRO: 0000000080050033

1.295271] CR2: 000000000000003c CR3: 0000000002646000 CR4: 00000000000406f0

1.295274] note: swapper/0[1] exited with irqs disabled

1.295280) Kernel panic not syncing: Attempted to kill init! exitcode=0x00

30009

1.297262] ---[ end Kernel panic not syncing: Attempted to kill init! exit

ode=0x00000009 1--- 

I am happy to provide more details and test any patches.

Arthur.