Re: [REGRESSION] iommu/amd: "Fix premature break in init_iommu_one()" causes early boot hang

From: Joerg Roedel

Date: Sat Aug 22 2026 - 01:49:24 EST

Adding Vasant.

On Fri, Aug 21, 2026 at 11:11:07PM +0200, Andreas Juch wrote:
> Hello,
>
> I noticed that one of my NixOS sytems failed to boot with kernel 6.18.40.
> The
> older 6.18.39 booted fine. A full git bisect of v6.18.39..v6.18.40
> identified
> the following commit as the first bad commit:
>
> dc266f6c4e2628576ab33042b6b2a12480220026
> iommu/amd: Fix premature break in init_iommu_one()
>
> The visible symptom is a black screen immediately after systemd-boot. The
> machine also remains unreachable over SSH and leaves no persistent journal
> entry
> for the failed boot. A reset or power cycle is required.
>
> I reverted that single commit, built the kernel again and the machine
> booted, so
> I'm quite sure that I found the right commit.
>
> System information:
>
> ASRockRack B550D4-4L
> BIOS P1.10 (06/28/2021)
>
> I'm no expert at all, but my research found that the following information
> might
> be relevant:
>
> journalctl -W -b -k --no-pager | rg -i 'AMD-Vi|AMD IOMMU|IOMMU|IVRS|IVHD'
> Aug 21 22:24:17 kernel: ACPI: IVRS 0x00000000BB062000 0000D0 (v02 AMD
> AmdTable 00000001 AMD 00000001)
> Aug 21 22:24:17 kernel: ACPI: Reserving IVRS table memory at [mem
> 0xbb062000-0xbb0620cf]
> Aug 21 22:24:17 kernel: AMD-Vi: Using global IVHD EFR:0x0, EFR2:0x0
> Aug 21 22:24:17 kernel: iommu: Default domain type: Translated
> Aug 21 22:24:17 kernel: iommu: DMA domain TLB invalidation policy: lazy
> mode
> Aug 21 22:24:17 kernel: pci 0000:00:01.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:00:01.2: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:00:02.0: Adding to iommu group 1
> Aug 21 22:24:17 kernel: pci 0000:00:03.0: Adding to iommu group 2
> Aug 21 22:24:17 kernel: pci 0000:00:04.0: Adding to iommu group 3
> Aug 21 22:24:17 kernel: pci 0000:00:05.0: Adding to iommu group 4
> Aug 21 22:24:17 kernel: pci 0000:00:07.0: Adding to iommu group 5
> Aug 21 22:24:17 kernel: pci 0000:00:07.1: Adding to iommu group 6
> Aug 21 22:24:17 kernel: pci 0000:00:08.0: Adding to iommu group 7
> Aug 21 22:24:17 kernel: pci 0000:00:08.1: Adding to iommu group 8
> Aug 21 22:24:17 kernel: pci 0000:00:14.0: Adding to iommu group 9
> Aug 21 22:24:17 kernel: pci 0000:00:14.3: Adding to iommu group 9
> Aug 21 22:24:17 kernel: pci 0000:00:18.0: Adding to iommu group 10
> Aug 21 22:24:17 kernel: pci 0000:00:18.1: Adding to iommu group 10
> Aug 21 22:24:17 kernel: pci 0000:00:18.2: Adding to iommu group 10
> Aug 21 22:24:17 kernel: pci 0000:00:18.3: Adding to iommu group 10
> Aug 21 22:24:17 kernel: pci 0000:00:18.4: Adding to iommu group 10
> Aug 21 22:24:17 kernel: pci 0000:00:18.5: Adding to iommu group 10
> Aug 21 22:24:17 kernel: pci 0000:00:18.6: Adding to iommu group 10
> Aug 21 22:24:17 kernel: pci 0000:00:18.7: Adding to iommu group 10
> Aug 21 22:24:17 kernel: pci 0000:02:00.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:02:00.1: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:02:00.2: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:20:00.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:20:01.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:20:02.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:20:03.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:20:04.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:20:08.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:20:09.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:21:00.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:22:00.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:23:00.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:24:00.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:25:00.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:29:00.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:2a:00.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:2b:00.0: Adding to iommu group 0
> Aug 21 22:24:17 kernel: pci 0000:2c:00.0: Adding to iommu group 11
> Aug 21 22:24:17 kernel: pci 0000:2d:00.0: Adding to iommu group 12
> Aug 21 22:24:17 kernel: pci 0000:2d:00.1: Adding to iommu group 13
> Aug 21 22:24:17 kernel: pci 0000:2d:00.3: Adding to iommu group 14
> Aug 21 22:24:17 kernel: pci 0000:2d:00.4: Adding to iommu group 15
> Aug 21 22:24:17 kernel: AMD-Vi: Extended features (0x58f77e022294881,
> 0x0): PreF GA GA_vAPIC
> Aug 21 22:24:17 kernel: AMD-Vi: Interrupt remapping enabled
>
> And the output of the decoded IVRS table, captured by `acpidump -n IVRS -b`:
>
> 00000000 49 56 52 53 d0 00 00 00 02 e2 41 4d 44 20 20 00 |IVRS......AMD
> .|
> 00000010 41 6d 64 54 61 62 6c 65 01 00 00 00 41 4d 44 20
> |AmdTable....AMD |
> 00000020 01 00 00 00 41 30 20 00 00 00 00 00 00 00 00 00 |....A0
> .........|
> 00000030 10 b0 48 00 02 00 40 00 00 00 50 fd 00 00 00 00
> |..H...@...P.....|
> 00000040 00 00 00 00 2e 8f 04 80 03 08 00 00 04 fe ff 00
> |................|
> 00000050 43 00 ff 00 00 a5 00 00 04 ff ff 00 00 00 00 00
> |C...............|
> 00000060 48 00 00 00 00 a0 00 02 48 00 00 d7 0d a0 00 01
> |H.......H.......|
> 00000070 48 00 00 00 0e 01 00 01 11 b0 58 00 02 00 40 00
> |H.........X...@.|
> 00000080 00 00 50 fd 00 00 00 00 00 00 00 00 00 02 04 00
> |..P.............|
> 00000090 5a 4a 29 22 ef 77 8f 05 00 00 00 00 00 00 00 00
> |ZJ)".w..........|
> 000000a0 03 08 00 00 04 fe ff 00 43 00 ff 00 00 a5 00 00
> |........C.......|
> 000000b0 04 ff ff 00 00 00 00 00 48 00 00 00 00 a0 00 02
> |........H.......|
> 000000c0 48 00 00 d7 0d a0 00 01 48 00 00 00 0e 01 00 01
> |H.......H.......|
> 000000d0
>
> The relevant part (after decoding with `iasl -d ivrs.dat`):
>
> [090h 0144 008h] EFR Image : 058F77EF22294A5A
>
> I'll provide any required details and test patches!
>
> Thanks for your work, it's very appreciated!
>
> Andreas
>