Issue #657 has been reported by Zoomm Deka.
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Bug #657: Alder Lake (x2e_n150) ACPI SCI (IRQ9) Interrupt Storm Escalation up
to 180k/sec on FreeBSD/OPNsense
https://ticket.coreboot.org/issues/657
* Author: Zoomm Deka
* Status: New
* Priority: Normal
* Target version: none
* Start date: 2026-07-10
* Affected versions: main
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Following up on the initial observation of interrupt storms on an Intel Alder
Lake platform (x2e_n150 mainboard) running FreeBSD 14 / OPNsense 26.7 with a
clean Libreboot/coreboot image:
UART0 (IRQ4): Disabling the serial port via loader hints
(hint.uart.0.disabled="1") successfully stopped the IRQ4 storm.
ACPI SCI (IRQ9): The ACPI storm on IRQ9 escalated drastically post-boot,
reaching a critical rate of 181,199 interrupts per second. Attempts to mitigate
this via software (e.g., changing the trigger to edge mode using
hw.acpi.sci.trigger="edge") were unsuccessful, indicating a persistent
level-triggered assertion from the hardware/firmware side.
This storm consumes significant CPU cycles, causing system degradation and
immediate hard locks when USB devices or higher IO loads are introduced.
Updated Data from vmstat -i:
Plaintext
interrupt total rate
irq9: acpi0 4241009125 181199
Context & Platform Details:
Mainboard: x2e_n150 (Intel Alder Lake)
OS: FreeBSD 14.1-RELEASE / OPNsense 26.7
Firmware: Clean Libreboot/coreboot compilation (includes commit 4988900789
soc/intel/alderlake: Fix PCI IRQ tables).
The issue points to an unhandled GPE (General Purpose Event) loop or incorrect
SCI routing configuration within the Alder Lake ACPI implementation for this
specific board variant.
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