Documentation/watchdog/hpwdt.txt

   1 Last reviewed: 05/20/2016
   2
   3                      HPE iLO NMI Watchdog Driver
   4               NMI sourcing for iLO based ProLiant Servers
   5                      Documentation and Driver by
   6                          Thomas Mingarelli
   7
   8  The HPE iLO 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  All references to iLO in this document imply it also works on iLO2 and all
  14  subsequent generations.
  15
  16  Watchdog functionality is enabled like any other common watchdog driver. That
  17  is, an application needs to be started that kicks off the watchdog timer. A
  18  basic application exists in the Documentation/watchdog/src directory called
  19  watchdog-test.c. Simply compile the C file and kick it off. If the system
  20  gets into a bad state and hangs, the HPE ProLiant iLO timer register will
  21  not be updated in a timely fashion and a hardware system reset (also known as
  22  an Automatic Server Recovery (ASR)) event will occur.
  23
  24  The hpwdt driver also has three (3) module parameters. They are the following:
  25
  26  soft_margin - allows the user to set the watchdog timer value.
  27                Default value is 30 seconds.
  28  allow_kdump - allows the user to save off a kernel dump image after an NMI.
  29                Default value is 1/ON
  30  nowayout    - basic watchdog parameter that does not allow the timer to
  31                be restarted or an impending ASR to be escaped.
  32                Default value is set when compiling the kernel. If it is set
  33                to "Y", then there is no way of disabling the watchdog once
  34                it has been started.
  35
  36  NOTE: More information about watchdog drivers in general, including the ioctl
  37        interface to /dev/watchdog can be found in
  38        Documentation/watchdog/watchdog-api.txt and Documentation/IPMI.txt.
  39
  40  The NMI sourcing capability is disabled by default due to the inability to
  41  distinguish between "NMI Watchdog Ticks" and "HW generated NMI events" in the
  42  Linux kernel. What this means is that the hpwdt nmi handler code is called
  43  each time the NMI signal fires off. This could amount to several thousands of
  44  NMIs in a matter of seconds. If a user sees the Linux kernel's "dazed and
  45  confused" message in the logs or if the system gets into a hung state, then
  46  the hpwdt driver can be reloaded.
  47
  48  1. If the kernel has not been booted with nmi_watchdog turned off then
  49     edit and place the nmi_watchdog=0 at the end of the currently booting
  50     kernel line. Depending on your Linux distribution and platform setup:
  51     For non-UEFI systems
  52        /boot/grub/grub.conf   or
  53        /boot/grub/menu.lst
  54     For UEFI systems
  55       /boot/efi/EFI/distroname/grub.conf   or
  56       /boot/efi/efi/distroname/elilo.conf
  57  2. reboot the sever
  58  3. Once the system comes up perform a modprobe -r hpwdt
  59  4. modprobe /lib/modules/`uname -r`/kernel/drivers/watchdog/hpwdt.ko
  60
  61  Now, the hpwdt can successfully receive and source the NMI and provide a log
  62  message that details the reason for the NMI (as determined by the HPE BIOS).
  63
  64  Below is a list of NMIs the HPE BIOS understands along with the associated
  65  code (reason):
  66
  67         No source found                00h
  68
  69         Uncorrectable Memory Error     01h
  70
  71         ASR NMI                        1Bh
  72
  73         PCI Parity Error               20h
  74
  75         NMI Button Press               27h
  76
  77         SB_BUS_NMI                     28h
  78
  79         ILO Doorbell NMI               29h
  80
  81         ILO IOP NMI                    2Ah
  82
  83         ILO Watchdog NMI               2Bh
  84
  85         Proc Throt NMI                 2Ch
  86
  87         Front Side Bus NMI             2Dh
  88
  89         PCI Express Error              2Fh
  90
  91         DMA controller NMI             30h
  92
  93         Hypertransport/CSI Error       31h
  94
  95
  96
  97  -- Tom Mingarelli