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: 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>hifive-unleashed-5.1
Jerry Hoemann
Wim Van Sebroeck
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@ -1,15 +1,12 @@
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Last reviewed: 05/20/2016
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Last reviewed: 08/20/2018
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HPE iLO NMI Watchdog Driver
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NMI sourcing for iLO based ProLiant Servers
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Documentation and Driver by
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Thomas Mingarelli
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for iLO based ProLiant Servers
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The HPE iLO NMI Watchdog driver is a kernel module that provides basic
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watchdog functionality and the added benefit of NMI sourcing. Both the
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watchdog functionality and the NMI sourcing capability need to be enabled
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by the user. Remember that the two modes are not dependent on one another.
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A user can have the NMI sourcing without the watchdog timer and vice-versa.
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watchdog functionality and handler for the iLO "Generate NMI to System"
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virtual button.
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All references to iLO in this document imply it also works on iLO2 and all
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subsequent generations.
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@ -21,12 +18,16 @@ Last reviewed: 05/20/2016
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not be updated in a timely fashion and a hardware system reset (also known as
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an Automatic Server Recovery (ASR)) event will occur.
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The hpwdt driver also has three (3) module parameters. They are the following:
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The hpwdt driver also has the following module parameters:
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soft_margin - allows the user to set the watchdog timer value.
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Default value is 30 seconds.
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allow_kdump - allows the user to save off a kernel dump image after an NMI.
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Default value is 1/ON
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timeout - an alias of soft_margin.
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pretimeout - allows the user to set the watchdog pretimeout value.
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This is the number of seconds before timeout when an
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NMI is delivered to the system. Setting the value to
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zero disables the pretimeout NMI.
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Default value is 9 seconds.
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nowayout - basic watchdog parameter that does not allow the timer to
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be restarted or an impending ASR to be escaped.
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Default value is set when compiling the kernel. If it is set
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@ -37,61 +38,29 @@ Last reviewed: 05/20/2016
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interface to /dev/watchdog can be found in
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Documentation/watchdog/watchdog-api.txt and Documentation/IPMI.txt.
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The NMI sourcing capability is disabled by default due to the inability to
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distinguish between "NMI Watchdog Ticks" and "HW generated NMI events" in the
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Linux kernel. What this means is that the hpwdt nmi handler code is called
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each time the NMI signal fires off. This could amount to several thousands of
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NMIs in a matter of seconds. If a user sees the Linux kernel's "dazed and
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confused" message in the logs or if the system gets into a hung state, then
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the hpwdt driver can be reloaded.
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Due to limitations in the iLO hardware, the NMI pretimeout if enabled,
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can only be set to 9 seconds. Attempts to set pretimeout to other
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non-zero values will be rounded, possibly to zero. Users should verify
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the pretimeout value after attempting to set pretimeout or timeout.
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1. If the kernel has not been booted with nmi_watchdog turned off then
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edit and place the nmi_watchdog=0 at the end of the currently booting
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kernel line. Depending on your Linux distribution and platform setup:
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For non-UEFI systems
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/boot/grub/grub.conf or
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/boot/grub/menu.lst
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For UEFI systems
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/boot/efi/EFI/distroname/grub.conf or
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/boot/efi/efi/distroname/elilo.conf
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2. reboot the sever
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3. Once the system comes up perform a modprobe -r hpwdt
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4. modprobe /lib/modules/`uname -r`/kernel/drivers/watchdog/hpwdt.ko
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Upon receipt of an NMI from the iLO, the hpwdt driver will initiate a
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panic. This is to allow for a crash dump to be collected. It is incumbent
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upon the user to have properly configured the system for kdump.
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Now, the hpwdt can successfully receive and source the NMI and provide a log
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message that details the reason for the NMI (as determined by the HPE BIOS).
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The default Linux kernel behavior upon panic is to print a kernel tombstone
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and loop forever. This is generally not what a watchdog user wants.
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Below is a list of NMIs the HPE BIOS understands along with the associated
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code (reason):
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For those wishing to learn more please see:
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Documentation/kdump/kdump.txt
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Documentation/admin-guide/kernel-parameters.txt (panic=)
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Your Linux Distribution specific documentation.
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No source found 00h
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If the hpwdt does not receive the NMI associated with an expiring timer,
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the iLO will proceed to reset the system at timeout if the timer hasn't
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been updated.
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Uncorrectable Memory Error 01h
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--
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ASR NMI 1Bh
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The HPE iLO NMI Watchdog Driver and documentation were originally developed
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by Tom Mingarelli.
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PCI Parity Error 20h
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NMI Button Press 27h
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SB_BUS_NMI 28h
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ILO Doorbell NMI 29h
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ILO IOP NMI 2Ah
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ILO Watchdog NMI 2Bh
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Proc Throt NMI 2Ch
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Front Side Bus NMI 2Dh
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PCI Express Error 2Fh
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DMA controller NMI 30h
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Hypertransport/CSI Error 31h
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-- Tom Mingarelli
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