Public bug reported:
Ubuntu 26.04 (resolute). linux-image-7.0.0-31, -34 and -38-generic panic
about 2 s into every boot on an AMD Ryzen 7 6800H (Rembrandt) mini PC.
7.0.0-30-generic is fine.
Symptom: NULL pointer dereference in propagate_entity_load_avg, reached
from pm_runtime_work -> pci_pm_runtime_suspend -> ACPI AML, followed by
"Kernel panic - not syncing: Attempted to kill the idle task!". The full
trace was captured with ramoops and is attached (panic-dmesg-ramoops.txt).
Cause: the stable backport of upstream commit 72780f796468 "PCI: Always
lift 2.5GT/s restriction in PCIe failed link retraining". Ubuntu imported
it in "Resolute update: upstream stable patchset 2026-07-21"
(LP: #2161462). The firmware clamps two GPP bridge ports to 2.5GT/s
(LnkCtl2 SpeedDis+). One of them is 00:02.3, an empty hotplug slot. The
quirk tries to retrain it, which fails ("00:02.3: retraining failed"), and
the panic follows. lspci -vvv for both ports is attached.
Fix: the upstream patch "PCI: Skip Target Speed quirk on clamped ports with
no link" (v3, patchwork 14725511,
https://lore.kernel.org/r/[email protected]),
applied to pci/misc for v7.3 with Cc: stable. On this machine it is a
complete fix: 7.0.0-38 plus that patch, unmodified, booted cleanly 6 out of
6 times and is now my daily kernel. Reverting pcie_failed_link_retrain()
to its pre-72780f796468 form also fixes it (5/5).
Request: please pick up the upstream fix, or revert 72780f796468, in the
7.0 kernels.
Reported upstream to linux-pci and [email protected] on
2026-10-04 (subject "[REGRESSION] PCI: 72780f796468 panics at boot on AMD
Rembrandt; fixed by ...").
Hardware: AMD Ryzen 7 6800H, AMI BIOS
RMB_P3_F7_20_EC0204_BI0005_AMI_LPD5_32G_28W_BI0005 (09/19/2025).
00:02.2 [1022:14ba] -> RTL8852BE Wi-Fi (link up at 2.5GT/s, Gen1-only device)
00:02.3 [1022:14ba] -> empty hotplug slot (no link)
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: regression-update resolute
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https://bugs.launchpad.net/bugs/2169492
Title:
7.0.0-31+ kernel panic at boot on AMD Rembrandt: "PCI: Always lift
2.5GT/s restriction" (72780f796468)
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