Supermicro BMC 看門狗導致的重啟
我最近購買了一塊 SuperMicro X10SLL-F 主機板，它內置了 BMC（Aspeed AST2400 晶片）。我想在伺服器上執行 linux 時使用內置的看門狗控制器（gentoo 加固）。
我在 BIOS 中啟用了看門狗功能，然後將主機板跳線從硬重置切換到 NMI（看門狗超時操作，用於測試目的以避免重新啟動）。關於軟體——我安裝並添加到預設執行級別看門狗程序（sys-apps/watchdog），該程序配置為每 10 秒 ping 一次看門狗設備（/dev/watchdog，存在）。看門狗超時設置為 250 秒。
程序顯然會看到看門狗硬體（啟用了 openipmi 的 ipmitool）：
# ipmitool mc watchdog get Watchdog Timer Use: SMS/OS (0x44) Watchdog Timer Is: Started/Running Watchdog Timer Actions: Hard Reset (0x01) Pre-timeout interval: 0 seconds Timer Expiration Flags: 0x10 Initial Countdown: 254 sec Present Countdown: 253 sec免費ipmi：
# bmc-watchdog --get Timer Use: SMS/OS Timer: Running Logging: Enabled Timeout Action: Hard Reset Pre-Timeout Interrupt: None Pre-Timeout Interval: 0 seconds Timer Use BIOS FRB2 Flag: Clear Timer Use BIOS POST Flag: Clear Timer Use BIOS OS Load Flag: Clear Timer Use BIOS SMS/OS Flag: Set Timer Use BIOS OEM Flag: Clear Initial Countdown: 254 seconds Current Countdown: 253 seconds但是，經過一段時間後，我得到了（上面的程序報告了良好的“目前倒計時”值）：
[ 294.107534] Uhhuh. NMI received for unknown reason 21 on CPU 0. [ 294.107998] Do you have a strange power saving mode enabled? [ 294.108437] Dazed and confused, but trying to continue這是 NMI，顯然是由看門狗超時引起的。機器硬重置發生後不到一分鐘。
哪裡有問題，應該往哪個方向去探勘？
編輯：與 ipmi 相關的核心消息：
[ 0.353090] ipmi message handler version 39.2 [ 0.353353] ipmi device interface [ 0.353623] IPMI System Interface driver. [ 0.353898] ipmi_si: probing via ACPI [ 0.354172] ipmi_si 00:08: [io 0x0ca2] regsize 1 spacing 1 irq 0 [ 0.354444] ipmi_si: Adding ACPI-specified kcs state machine [ 0.354790] ipmi_si: probing via SMBIOS [ 0.355051] ipmi_si: SMBIOS: io 0xca2 regsize 1 spacing 1 irq 0 [ 0.355317] ipmi_si: Adding SMBIOS-specified kcs state machine duplicate interface [ 0.355836] ipmi_si: probing via SPMI [ 0.356095] ipmi_si: SPMI: io 0xca2 regsize 1 spacing 1 irq 0 [ 0.356362] ipmi_si: Adding SPMI-specified kcs state machine duplicate interface [ 0.356906] ipmi_si: Trying ACPI-specified kcs state machine at i/o address 0xca2, slave address 0x0, irq 0 [ 0.390536] ipmi_si: The BMC does not support clearing the recv irq bit, compensating, but the BMC needs to be fixed. [ 0.418476] ipmi_si 00:08: Found new BMC (man_id: 0x002a7c, prod_id: 0x0801, dev_id: 0x20) [ 0.419004] ipmi_si 00:08: IPMI kcs interface initialized [ 0.419272] IPMI SSIF Interface driver [ 0.420350] IPMI Watchdog: driver initialized [ 0.420635] Copyright (C) 2004 MontaVista Software - IPMI Powerdown via sys_reboot. [ 0.421444] IPMI poweroff: ATCA Detect mfg 0x2A7C prod 0x801 [ 0.421710] IPMI poweroff: Found a chassis style poweroff function編輯：我嘗試使用配置為“-u 4 -p 2 -a 0 -F -P -L -O -i 300 -e 10”的 bmc-watchdog。所以只有 SMS/OS 時間在使用，預超時中斷設置為 NMI，超時操作設置為 NONE：
# bmc-watchdog --get Timer Use: SMS/OS Timer: Running Logging: Enabled Timeout Action: None Pre-Timeout Interrupt: NMI / Diagnostic Interrupt Pre-Timeout Interval: 0 seconds Timer Use BIOS FRB2 Flag: Clear Timer Use BIOS POST Flag: Clear Timer Use BIOS OS Load Flag: Clear Timer Use BIOS SMS/OS Flag: Set Timer Use BIOS OEM Flag: Clear Initial Countdown: 300 seconds Current Countdown: 290 seconds但這根本沒有改變。
編輯。此外，當我通過將 \0x00 回顯到 /dev/watchdog 來觸發看門狗計時器，然後將其保持不變時——系統在預設的 10 秒超時後正確重新啟動。所以看門狗工作得很好，但在啟動系統重新啟動後正好 350 秒。
編輯。我檢查了 BMC 系統事件日誌 (SEL) 並在重新啟動後發現：
Sensor #202 | Watchdog 2 | Assertion Event | Timer interrupt ; Timer use at expiration = SMS/OS ; Interrupt type = none Sensor #202 | Watchdog 2 | Assertion Event | Timer expired, status only ; Timer use at expiration = SMS/OS ; Interrupt type = none這裡有趣的是——該事件被標記為“僅狀態”。即便如此，系統也會重新啟動。當我故意觸發看門狗超時時，日誌是不同的：
Sensor #202 | Watchdog 2 | Assertion Event | Timer interrupt ; Timer use at expiration = SMS/OS ; Interrupt type = none Sensor #202 | Watchdog 2 | Assertion Event | Hard Reset ; Timer use at expiration = SMS/OS ; Interrupt type = none
最後，我找到了一個有點奇怪的解決方案：讓看門狗跳線（JWD1）保持打開狀態（既沒有選擇 NMI 也沒有選擇硬重置）。看門狗在 BIOS 設置中啟用。
在這種情況下，看門狗按預期工作——系統穩定了 25 分鐘，bmc-watchdog 執行並在看門狗程序終止後重新啟動。