Commit 18bd1963 authored by Jerry Hoemann's avatar Jerry Hoemann Committed by Wim Van Sebroeck
Browse files

watchdog: hpwdt: Update Driver Documentation. 



Remove references to deprecated features like NMI sourcing
and obsoleted module parameters.

Add details concerning new module parameter pretimeout and tips
to programming it.

Signed-off-by: default avatarJerry Hoemann <jerry.hoemann@hpe.com>
Reviewed-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarWim Van Sebroeck <wim@linux-watchdog.org>
parent e1c7f79e

Documentation/watchdog/hpwdt.txt

+31 −62
Original line number Diff line number Diff line 
Last reviewed: 05/20/2016

Last reviewed: 08/20/2018



                     HPE iLO NMI Watchdog Driver

              NMI sourcing for iLO based ProLiant Servers

                     Documentation and Driver by

                         Thomas Mingarelli

                   for iLO based ProLiant Servers



 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.

 watchdog functionality and handler for the iLO "Generate NMI to System"

 virtual button.



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

 subsequent generations.
@@ -21,12 +18,16 @@ Last reviewed: 05/20/2016 
 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 three (3) module parameters. They are the following:

 The hpwdt driver also has the following module parameters:



 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

 timeout     - an alias of soft_margin.

 pretimeout  - allows the user to set the watchdog pretimeout value.

               This is the number of seconds before timeout when an

               NMI is delivered to the system. Setting the value to

               zero disables the pretimeout NMI.

               Default value is 9 seconds.

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

               be restarted or an impending ASR to be escaped.

               Default value is set when compiling the kernel. If it is set
@@ -37,61 +38,29 @@ Last reviewed: 05/20/2016 
       interface to /dev/watchdog can be found in

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



 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.



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

    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 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 HPE BIOS).



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

 code (reason):



	No source found                00h



	Uncorrectable Memory Error     01h



	ASR NMI                        1Bh



	PCI Parity Error               20h



	NMI Button Press               27h



	SB_BUS_NMI                     28h



	ILO Doorbell NMI               29h



	ILO IOP NMI                    2Ah



	ILO Watchdog NMI               2Bh



	Proc Throt NMI                 2Ch

 Due to limitations in the iLO hardware, the NMI pretimeout if enabled,

 can only be set to 9 seconds.  Attempts to set pretimeout to other

 non-zero values will be rounded, possibly to zero.  Users should verify

 the pretimeout value after attempting to set pretimeout or timeout.



	Front Side Bus NMI             2Dh

 Upon receipt of an NMI from the iLO, the hpwdt driver will initiate a

 panic. This is to allow for a crash dump to be collected.  It is incumbent

 upon the user to have properly configured the system for kdump.



	PCI Express Error              2Fh

 The default Linux kernel behavior upon panic is to print a kernel tombstone

 and loop forever.  This is generally not what a watchdog user wants.



	DMA controller NMI             30h

 For those wishing to learn more please see:

	Documentation/kdump/kdump.txt

	Documentation/admin-guide/kernel-parameters.txt (panic=)

	Your Linux Distribution specific documentation.



	Hypertransport/CSI Error       31h

 If the hpwdt does not receive the NMI associated with an expiring timer,

 the iLO will proceed to reset the system at timeout if the timer hasn't

 been updated.



--



 The HPE iLO NMI Watchdog Driver and documentation were originally developed

 by Tom Mingarelli.

 -- Tom Mingarelli

CRA Git | Maintained and supported by SUSTech CRA and CCSE