Documentation/watchdog/hpwdt.txt

   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 <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 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     (thomas.mingarelli@hp.com)