watchdog: hpwdt: Adjust documentation to match latest kernel module parameters.

Last reviewed: 06/02/2009

Last reviewed: 04/04/2016

                     HP iLO2 NMI Watchdog Driver

              NMI sourcing for iLO2 based ProLiant Servers

                     HPE iLO NMI Watchdog Driver

              NMI sourcing for iLO based ProLiant Servers

                     Documentation and Driver by

              Thomas Mingarelli <thomas.mingarelli@hp.com>

              Thomas Mingarelli <thomas.mingarelli@hpe.com>

 The HP iLO2 NMI Watchdog driver is a kernel module that provides basic

 The HPE iLO NMI Watchdog driver is a kernel module that provides basic

 watchdog functionality and the added benefit of NMI sourcing. Both the

 watchdog functionality and the NMI sourcing capability need to be enabled

 by the user. Remember that the two modes are not dependent on one another.

 A user can have the NMI sourcing without the watchdog timer and vice-versa.

 All references to iLO in this document imply it also works on iLO2 and all

 subsequent generations.

 Watchdog functionality is enabled like any other common watchdog driver. That

 is, an application needs to be started that kicks off the watchdog timer. A

 basic application exists in the Documentation/watchdog/src directory called

 watchdog-test.c. Simply compile the C file and kick it off. If the system

 gets into a bad state and hangs, the HP ProLiant iLO 2 timer register will

 gets into a bad state and hangs, the HPE ProLiant iLO timer register will

 not be updated in a timely fashion and a hardware system reset (also known as

 an Automatic Server Recovery (ASR)) event will occur.

 The hpwdt driver also has four (4) module parameters. They are the following:

 The hpwdt driver also has three (3) module parameters. They are the following:

 soft_margin - allows the user to set the watchdog timer value

 allow_kdump - allows the user to save off a kernel dump image after an NMI

 soft_margin - allows the user to set the watchdog timer value.

               Default value is 30 seconds.

 allow_kdump - allows the user to save off a kernel dump image after an NMI.

               Default value is 1/ON

 nowayout    - basic watchdog parameter that does not allow the timer to

               be restarted or an impending ASR to be escaped.

 priority    - determines whether or not the hpwdt driver is first on the

               die_notify list to handle NMIs or last. The default value

               for this module parameter is 0 or LAST. If the user wants to

               enable NMI sourcing then reload the hpwdt driver with

               priority=1 (and boot with nmi_watchdog=0).

               Default value is set when compiling the kernel. If it is set

               to "Y", then there is no way of disabling the watchdog once

               it has been started.

 NOTE: More information about watchdog drivers in general, including the ioctl

       interface to /dev/watchdog can be found in

       Documentation/watchdog/watchdog-api.txt and Documentation/IPMI.txt.

 The priority parameter was introduced due to other kernel software that relied

 on handling NMIs (like oprofile). Keeping hpwdt's priority at 0 (or LAST)

 enables the users of NMIs for non critical events to be work as expected.

 The NMI sourcing capability is disabled by default due to the inability to

 distinguish between "NMI Watchdog Ticks" and "HW generated NMI events" in the

 Linux kernel. What this means is that the hpwdt nmi handler code is called

 each time the NMI signal fires off. This could amount to several thousands of

 NMIs in a matter of seconds. If a user sees the Linux kernel's "dazed and

 confused" message in the logs or if the system gets into a hung state, then

 the hpwdt driver can be reloaded with the "priority" module parameter set

 (priority=1).

 the hpwdt driver can be reloaded.

 1. If the kernel has not been booted with nmi_watchdog turned off then

    edit /boot/grub/menu.lst and place the nmi_watchdog=0 at the end of the

    currently booting kernel line.

    edit and place the nmi_watchdog=0 at the end of the currently booting

    kernel line. Depending on your Linux distribution and platform setup:

    For non-UEFI systems

       /boot/grub/grub.conf   or

       /boot/grub/menu.lst

    For UEFI systems

      /boot/efi/EFI/distroname/grub.conf   or

      /boot/efi/efi/distroname/elilo.conf

 2. reboot the sever

 3. Once the system comes up perform a rmmod hpwdt

 4. insmod /lib/modules/`uname -r`/kernel/drivers/char/watchdog/hpwdt.ko priority=1

 3. Once the system comes up perform a modprobe -r hpwdt

 4. modprobe /lib/modules/`uname -r`/kernel/drivers/watchdog/hpwdt.ko

 Now, the hpwdt can successfully receive and source the NMI and provide a log

 message that details the reason for the NMI (as determined by the HP BIOS).

 message that details the reason for the NMI (as determined by the HPE BIOS).

 Below is a list of NMIs the HP BIOS understands along with the associated

 Below is a list of NMIs the HPE BIOS understands along with the associated

 code (reason):

	No source found                00h

 -- Tom Mingarelli

    (thomas.mingarelli@hp.com)

    (thomas.mingarelli@hpe.com)