Public bug reported:
Title: iwlwifi (AX101 / so-a0-hr-b0 / fw 89) — reproducible
NMI_INTERRUPT_UMAC_FATAL firmware
assert on 5 GHz DFS channels: 293 asserts / 50 boots over 11 months, 84%
clustered
20:00–24:00, peak at 21:00
================================================================================
SUMMARY
================================================================================
The iwlwifi firmware reproducibly asserts (NMI_INTERRUPT_UMAC_FATAL /
ADVANCED_SYSASSERT)
when associated to an AP on a 5 GHz DFS channel, cascading into a device-reset
storm
("Too many device errors - delay next reset") and a full desktop freeze
requiring a hard
power-cycle. Over 11 months of daily use: 293 asserts across 50 boots
(2025-08-15 →
2026-07-26), with 84% occurring between 20:00–24:00 local and 53% at the 21:00
hour alone —
consistent with elevated evening DFS radar activity. Zero asserts on non-DFS
channels or
2.4 GHz.
================================================================================
HARDWARE
================================================================================
- Laptop: ASUS Vivobook X1504VA
- CPU: Intel Core i3-1315U (Raptor Lake-U, 13th Gen)
- Wi-Fi: Intel AX101 CNVi, PCI 0000:00:14.3, RF module so-a0-hr-b0 (HR1 B3)
================================================================================
SOFTWARE
================================================================================
- OS: Ubuntu 26.04 (development branch)
- Kernel: 7.0.0-28-generic
- Driver: iwlwifi / iwlmvm
- Firmware: iwlwifi-so-a0-hr-b0-89.ucode, version 89.123cf747.0
(latest available; driver requests API 89 only, no fallback)
================================================================================
ASSERT SIGNATURES
================================================================================
iwlwifi 0000:00:14.3: Microcode SW error detected. Restarting 0x0.
iwlwifi 0000:00:14.3: 0x00000071 | NMI_INTERRUPT_UMAC_FATAL
iwlwifi 0000:00:14.3: 0x2010120E | ADVANCED_SYSASSERT
iwlwifi 0000:00:14.3: 0x00000B03 | IML/ROM error/state
iwlwifi 0000:00:14.3: 0x00000090 | IML/ROM WFPM_AUTH_KEY_0
iwlwifi 0000:00:14.3: 0x60000000 | FSEQ_ERROR_CODE
iwlwifi 0000:00:14.3: Too many device errors - delay next reset
================================================================================
STATISTICAL EVIDENCE (persistent journald, 50 affected boots)
================================================================================
- Range: 2025-08-15 21:22 → 2026-07-26 10:51
- Total NMI_INTERRUPT_UMAC_FATAL events: 293
- Hour-of-day distribution:
21:00 -> 154 (53%)
22:00 -> 34
23:00 -> 32
20:00 -> 27
17:00 -> 26 ┐
10:00 -> 12 ├ daytime remainder = only days spent on-site at the
affected location
15:00 -> 8 ┘
- 247/293 (84%) fall in 20:00–24:00.
- Signal quality excellent (-44 dBm) — not a weak-signal issue.
================================================================================
TRIGGER / REPRODUCTION
================================================================================
- Occurs only on a 5 GHz DFS channel (confirmed on channel 112 / 5560 MHz).
- A radar-related channel switch (CSA) — or a manual 5→2.4 GHz band switch while
associated — deterministically triggers the assert; the manual case caused an
immediate full desktop freeze + reboot.
- The strong evening clustering is consistent with elevated DFS radar activity
at that time.
================================================================================
WHEN IT DOES NOT HAPPEN
================================================================================
- Non-DFS 5 GHz channel (36–48 / 149–161): zero asserts over 5+ hours.
- 2.4 GHz (channel 11): zero asserts.
- AP configured with skip-dfs-channels=all: never occurs.
================================================================================
IMPACT
================================================================================
After the assert cascade the device enters permanent reset failure, Wi-Fi
drops, and
the GNOME desktop hangs. A warm reboot does NOT recover the CNVi (it is not
power-cycled);
a full cold poweroff is required to restore Wi-Fi.
================================================================================
RULED OUT (verified via journalctl across affected boots)
================================================================================
- GPU/i915 hang, kernel panic/lockup/RCU stall, MCE/hardware, thermal, OOM —
all absent.
- The only recurring fault is iwlwifi.
- Not mitigated by: bt_coex_active=0, disable_11ax=1, or power-management tweaks
(iwlmvm power_scheme=1, wifi.powersave off).
- Firmware downgrade is impossible (driver requests API 89 only).
================================================================================
WORKAROUND
================================================================================
Force the client to 2.4 GHz (separate SSID), or pin the AP to a fixed non-DFS 5
GHz
channel. The provider (Vodafone) router's 5 GHz channel is locked to
"automatic", so
channel pinning was not possible on that device.
================================================================================
EXPECTED BEHAVIOR
================================================================================
The firmware should handle a DFS radar event / channel-switch announcement (CSA)
gracefully, without a fatal UMAC assert and device-reset storm.
================================================================================
HOW TO FILE
================================================================================
Ubuntu (auto-collects hardware, dmesg, versions):
ubuntu-bug linux
Upstream (firmware fix):
bugzilla.kernel.org -> Product: Drivers, Component: network-wireless
(iwlwifi)
or [email protected]
Attach: iwlwifi-bug-attachment.txt (per-boot assert summary + full assert log
lines)
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-7.0.0-28-generic 7.0.0-28.28
ProcVersionSignature: Ubuntu 7.0.0-28.28-generic 7.0.12
Uname: Linux 7.0.0-28-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: taszilo 5120 F.... wireplumber
/dev/snd/seq: taszilo 5103 F.... pipewire
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Sun Jul 26 11:23:59 2026
InstallationDate: Installed on 2025-06-13 (408 days ago)
InstallationMedia: Ubuntu 25.04 "Plucky Puffin" - Release amd64 (20250415.3)
MachineType: ASUSTeK COMPUTER INC. Vivobook_ASUSLaptop X1504VA_X1504VA
ProcEnviron:
LANG=hu_HU.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-28-generic
root=UUID=934c7500-722d-4723-8f37-6f28418723dd ro quiet splash
crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M
SourcePackage: linux
UpgradeStatus: Upgraded to resolute on 2026-06-13 (43 days ago)
dmi.bios.date: 03/13/2024
dmi.bios.release: 5.27
dmi.bios.vendor: American Megatrends International, LLC.
dmi.bios.version: X1504VA.304
dmi.board.asset.tag: ATN12345678901234567
dmi.board.name: X1504VA
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: 1.0
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK COMPUTER INC.
dmi.chassis.version: 1.0
dmi.modalias:
dmi:bvnAmericanMegatrendsInternational,LLC.:bvrX1504VA.304:bd03/13/2024:br5.27:svnASUSTeKCOMPUTERINC.:pnVivobook_ASUSLaptopX1504VA_X1504VA:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnX1504VA:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:sku:pfaVivobook:
dmi.product.family: Vivobook
dmi.product.name: Vivobook_ASUSLaptop X1504VA_X1504VA
dmi.product.version: 1.0
dmi.sys.vendor: ASUSTeK COMPUTER INC.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
** Attachment added: "iwlwifi-bug-attachment.txt"
https://bugs.launchpad.net/bugs/2161831/+attachment/5986590/+files/iwlwifi-bug-attachment.txt
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https://bugs.launchpad.net/bugs/2161831
Title:
iwlwifi (AX101/so-a0-hr-b0/fw 89) NMI_INTERRUPT_UMAC_FATAL firmware
assert on 5 GHz DFS channels
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