Public bug reported:
Hardware: Dell Pro Max Tower T2 (Arrow Lake)
Current Working Kernel: 6.14.0-1014-oem
Broken Kernel: 6.17.0-1020.20-oem
Summary:
There is a kernel regression in the VMD driver (vmd.ko) affecting new Dell
Arrow Lake systems with dual NVMe configurations. The hardware reports a Bus
Offset of 3. While the 6.14-oem kernel correctly handles this, the fix appears
to have been dropped in the 6.17-oem branch.
Symptoms:
When booting kernel 6.17, the system fails to mount the root filesystem and
drops to an initramfs shell. The dmesg logs show:
"vmd 0000:00:0e.0: Unknown Bus Offset Setting (3)"
Evidence of Regression (Source Code Audit):
In the working 6.14-oem source (drivers/pci/controller/vmd.c), Case 3 is
correctly implemented to map both VMD_BUS_0 and VMD_BUS_1:
713: case 3:
714- if (!(features & VMD_FEAT_HAS_PCH_ROOTBUS)) {
...
721- vmd->busn_start[VMD_BUS_0] = 224; // (0xE0)
723- vmd->busn_start[VMD_BUS_1] = 225; // (0xE1)
However, in the linux-oem-6.17.0-1020.20 source, a grep for "case 3:" in
drivers/pci/controller/vmd.c returns NO results. The driver hits the
'default' case and returns -ENODEV, causing the storage controller to
fail. This dropped patch causes the system to be unbootable on the newer
OEM kernel.
Steps to Reproduce:
- Install Ubuntu 24.04 using the official Dell OEM recovery image (which
defaults to the functional 6.14.0-1014-oem kernel).
- Verify that both physical NVMe drives are visible and the system boots
correctly.
- Perform a standard sudo apt update && sudo apt upgrade, which pulls in the
linux-image-oem-24.04c (version 6.17.0-1020-oem).
- Reboot the system into the 6.17 kernel.
- Observation: The system fails to mount the root partition on the second disk
and drops to an initramfs shell because the VMD controller fails to initialize
(Bus Offset 3 error).
---
output for 'lspci -nn | grep VMD' :
0000:00:01.0 System peripheral [0880]: Intel Corporation RST VMD Managed
Controller [8086:09ab]
0000:80:17.0 System peripheral [0880]: Intel Corporation RST VMD Managed
Controller [8086:09ab]
10000:80:1b.0 System peripheral [0880]: Intel Corporation RST VMD Managed
Controller [8086:09ab]
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-6.14.0-1014-oem 6.14.0-1014.14
ProcVersionSignature: Ubuntu 6.14.0-1014.14-oem 6.14.11
Uname: Linux 6.14.0-1014-oem x86_64
ApportVersion: 2.28.1-0ubuntu3.8
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: local 2603 F.... wireplumber
/dev/snd/seq: local 2599 F.... pipewire
CRDA: N/A
CasperMD5CheckMismatches: ./casper/initrd
./casper/minimal.standard.live.hotfix.manifest
./casper/minimal.standard.live.hotfix.size ./casper/minimal.standard.live.size
./casper/minimal.manifest ./casper/minimal.standard.manifest
./casper/minimal.standard.size ./casper/minimal.hotfix.size
./casper/minimal.standard.live.hotfix.squashfs
./casper/minimal.standard.hotfix.squashfs ./casper/minimal.standard.hotfix.size
./casper/minimal.hotfix.squashfs ./casper/minimal.standard.live.manifest
./casper/minimal.size ./boot/grub/grub.cfg
CasperMD5CheckResult: fail
Date: Wed May 13 16:02:40 2026
DistributionChannelDescriptor:
# This is the distribution channel descriptor for Ubuntu 24.04 for Dell
# For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
canonical-oem-somerville-noble-oem-24.04c-20251022-81
InstallationDate: Installed on 2026-05-13 (0 days ago)
InstallationMedia: Ubuntu OEM 24.04.3 LTS "Noble Numbat" - Release amd64
(20251022)
IwConfig:
lo no wireless extensions.
enp128s31f6 no wireless extensions.
Lsusb:
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 002: ID 05e3:0610 Genesys Logic, Inc. Hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Lsusb-t:
/: Bus 001.Port 001: Dev 001, Class=root_hub, Driver=xhci_hcd/1p, 480M
/: Bus 002.Port 001: Dev 001, Class=root_hub, Driver=xhci_hcd/2p, 20000M/x2
/: Bus 003.Port 001: Dev 001, Class=root_hub, Driver=xhci_hcd/16p, 480M
|__ Port 005: Dev 002, If 0, Class=Hub, Driver=hub/2p, 480M
/: Bus 004.Port 001: Dev 001, Class=root_hub, Driver=xhci_hcd/8p, 20000M/x2
MachineType: Dell Inc. Dell Pro Max Tower T2 FCT2250
ProcEnviron:
LANG=C.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.14.0-1014-oem
root=UUID=f0aafc54-74e7-4b9c-bc81-28e5a391a43b ro quiet splash vt.handoff=7
RebootRequiredPkgs: Error: path contained symlinks.
RelatedPackageVersions:
linux-restricted-modules-6.14.0-1014-oem N/A
linux-backports-modules-6.14.0-1014-oem N/A
linux-firmware 20240318.git3b128b60-0ubuntu2.19
RfKill:
SourcePackage: linux-oem-6.14
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 12/31/2025
dmi.bios.release: 1.12
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.12.0
dmi.board.name: 0D8XDK
dmi.board.vendor: Dell Inc.
dmi.board.version: A01
dmi.chassis.asset.tag: HN602564
dmi.chassis.type: 3
dmi.chassis.vendor: Dell Inc.
dmi.ec.firmware.release: 1.17
dmi.modalias:
dmi:bvnDellInc.:bvr1.12.0:bd12/31/2025:br1.12:efr1.17:svnDellInc.:pnDellProMaxTowerT2FCT2250:pvr:rvnDellInc.:rn0D8XDK:rvrA01:cvnDellInc.:ct3:cvr:sku0CE1:
dmi.product.family: Dell Pro Max Desktops
dmi.product.name: Dell Pro Max Tower T2 FCT2250
dmi.product.sku: 0CE1
dmi.sys.vendor: Dell Inc.
** Affects: linux-oem-6.14 (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble
** Attachment added: "case3.png"
https://bugs.launchpad.net/bugs/2152561/+attachment/5970062/+files/case3.png
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https://bugs.launchpad.net/bugs/2152561
Title:
[Regression] VMD Arrow Lake support (Bus Offset 3) missing in linux-
oem-6.17.0-1020.20
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