Based on kernel version 4.2. Page generated on 2015-09-09 12:15 EST.
1 Last reviewed: 06/02/2009 2 3 HP iLO2 NMI Watchdog Driver 4 NMI sourcing for iLO2 based ProLiant Servers 5 Documentation and Driver by 6 Thomas Mingarelli <firstname.lastname@example.org> 7 8 The HP iLO2 NMI Watchdog driver is a kernel module that provides basic 9 watchdog functionality and the added benefit of NMI sourcing. Both the 10 watchdog functionality and the NMI sourcing capability need to be enabled 11 by the user. Remember that the two modes are not dependent on one another. 12 A user can have the NMI sourcing without the watchdog timer and vice-versa. 13 14 Watchdog functionality is enabled like any other common watchdog driver. That 15 is, an application needs to be started that kicks off the watchdog timer. A 16 basic application exists in the Documentation/watchdog/src directory called 17 watchdog-test.c. Simply compile the C file and kick it off. If the system 18 gets into a bad state and hangs, the HP ProLiant iLO 2 timer register will 19 not be updated in a timely fashion and a hardware system reset (also known as 20 an Automatic Server Recovery (ASR)) event will occur. 21 22 The hpwdt driver also has four (4) module parameters. They are the following: 23 24 soft_margin - allows the user to set the watchdog timer value 25 allow_kdump - allows the user to save off a kernel dump image after an NMI 26 nowayout - basic watchdog parameter that does not allow the timer to 27 be restarted or an impending ASR to be escaped. 28 priority - determines whether or not the hpwdt driver is first on the 29 die_notify list to handle NMIs or last. The default value 30 for this module parameter is 0 or LAST. If the user wants to 31 enable NMI sourcing then reload the hpwdt driver with 32 priority=1 (and boot with nmi_watchdog=0). 33 34 NOTE: More information about watchdog drivers in general, including the ioctl 35 interface to /dev/watchdog can be found in 36 Documentation/watchdog/watchdog-api.txt and Documentation/IPMI.txt. 37 38 The priority parameter was introduced due to other kernel software that relied 39 on handling NMIs (like oprofile). Keeping hpwdt's priority at 0 (or LAST) 40 enables the users of NMIs for non critical events to be work as expected. 41 42 The NMI sourcing capability is disabled by default due to the inability to 43 distinguish between "NMI Watchdog Ticks" and "HW generated NMI events" in the 44 Linux kernel. What this means is that the hpwdt nmi handler code is called 45 each time the NMI signal fires off. This could amount to several thousands of 46 NMIs in a matter of seconds. If a user sees the Linux kernel's "dazed and 47 confused" message in the logs or if the system gets into a hung state, then 48 the hpwdt driver can be reloaded with the "priority" module parameter set 49 (priority=1). 50 51 1. If the kernel has not been booted with nmi_watchdog turned off then 52 edit /boot/grub/menu.lst and place the nmi_watchdog=0 at the end of the 53 currently booting kernel line. 54 2. reboot the sever 55 3. Once the system comes up perform a rmmod hpwdt 56 4. insmod /lib/modules/`uname -r`/kernel/drivers/char/watchdog/hpwdt.ko priority=1 57 58 Now, the hpwdt can successfully receive and source the NMI and provide a log 59 message that details the reason for the NMI (as determined by the HP BIOS). 60 61 Below is a list of NMIs the HP BIOS understands along with the associated 62 code (reason): 63 64 No source found 00h 65 66 Uncorrectable Memory Error 01h 67 68 ASR NMI 1Bh 69 70 PCI Parity Error 20h 71 72 NMI Button Press 27h 73 74 SB_BUS_NMI 28h 75 76 ILO Doorbell NMI 29h 77 78 ILO IOP NMI 2Ah 79 80 ILO Watchdog NMI 2Bh 81 82 Proc Throt NMI 2Ch 83 84 Front Side Bus NMI 2Dh 85 86 PCI Express Error 2Fh 87 88 DMA controller NMI 30h 89 90 Hypertransport/CSI Error 31h 91 92 93 94 -- Tom Mingarelli 95 (email@example.com)