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1Last 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 <thomas.mingarelli@hp.com>
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 dependant 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 three (3) 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
29 NOTE: More information about watchdog drivers in general, including the ioctl
30 interface to /dev/watchdog can be found in
31 Documentation/watchdog/watchdog-api.txt and Documentation/IPMI.txt.
32
33 The NMI sourcing capability is disabled when the driver discovers that the
34 nmi_watchdog is turned on (nmi_watchdog = 1). This is due to the inability to
35 distinguish between "NMI Watchdog Ticks" and "HW generated NMI events" in the
36 Linux kernel. What this means is that the hpwdt nmi handler code is called
37 each time the NMI signal fires off. This could amount to several thousands of
38 NMIs in a matter of seconds. If a user sees the Linux kernel's "dazed and
39 confused" message in the logs or if the system gets into a hung state, then
40 the user should reboot with nmi_watchdog=0.
41
42 1. If the kernel has not been booted with nmi_watchdog turned off then
43 edit /boot/grub/menu.lst and place the nmi_watchdog=0 at the end of the
44 currently booting kernel line.
45 2. reboot the sever
46
47 Now, the hpwdt can successfully receive and source the NMI and provide a log
48 message that details the reason for the NMI (as determined by the HP BIOS).
49
50 Below is a list of NMIs the HP BIOS understands along with the associated
51 code (reason):
52
53 No source found 00h
54
55 Uncorrectable Memory Error 01h
56
57 ASR NMI 1Bh
58
59 PCI Parity Error 20h
60
61 NMI Button Press 27h
62
63 SB_BUS_NMI 28h
64
65 ILO Doorbell NMI 29h
66
67 ILO IOP NMI 2Ah
68
69 ILO Watchdog NMI 2Bh
70
71 Proc Throt NMI 2Ch
72
73 Front Side Bus NMI 2Dh
74
75 PCI Express Error 2Fh
76
77 DMA controller NMI 30h
78
79 Hypertransport/CSI Error 31h
80
81
82
83 -- Tom Mingarelli
84 (thomas.mingarelli@hp.com)