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watchdog: hpwdt: Update Driver Documentation.

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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: Jerry Hoemann <jerry.hoemann@hpe.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
This commit is contained in:
Jerry Hoemann 2018-08-20 13:31:23 -06:00 committed by Wim Van Sebroeck
parent e1c7f79ea5
commit 18bd1963ae
1 changed files with 31 additions and 62 deletions
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93
Documentation/watchdog/hpwdt.txt
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@ -1,15 +1,12 @@
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.
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.
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
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.
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).
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.
Below is a list of NMIs the HPE BIOS understands along with the associated
code (reason):
For those wishing to learn more please see:
Documentation/kdump/kdump.txt
Documentation/admin-guide/kernel-parameters.txt (panic=)
Your Linux Distribution specific documentation.
No source found 00h
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.
Uncorrectable Memory Error 01h
--
ASR NMI 1Bh
The HPE iLO NMI Watchdog Driver and documentation were originally developed
by Tom Mingarelli.
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
Front Side Bus NMI 2Dh
PCI Express Error 2Fh
DMA controller NMI 30h
Hypertransport/CSI Error 31h
-- Tom Mingarelli