96 lines
3.9 KiB
Plaintext
96 lines
3.9 KiB
Plaintext
Last reviewed: 06/02/2009
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HP iLO2 NMI Watchdog Driver
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NMI sourcing for iLO2 based ProLiant Servers
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Documentation and Driver by
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Thomas Mingarelli <thomas.mingarelli@hp.com>
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The HP iLO2 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 is enabled like any other common watchdog driver. That
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is, an application needs to be started that kicks off the watchdog timer. A
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basic application exists in the Documentation/watchdog/src directory called
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watchdog-test.c. Simply compile the C file and kick it off. If the system
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gets into a bad state and hangs, the HP ProLiant iLO 2 timer register will
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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 four (4) module parameters. They are the following:
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soft_margin - allows the user to set the watchdog timer value
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allow_kdump - allows the user to save off a kernel dump image after an NMI
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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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priority - determines whether or not the hpwdt driver is first on the
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die_notify list to handle NMIs or last. The default value
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for this module parameter is 0 or LAST. If the user wants to
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enable NMI sourcing then reload the hpwdt driver with
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priority=1 (and boot with nmi_watchdog=0).
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NOTE: More information about watchdog drivers in general, including the ioctl
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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 priority parameter was introduced due to other kernel software that relied
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on handling NMIs (like oprofile). Keeping hpwdt's priority at 0 (or LAST)
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enables the users of NMIs for non critical events to be work as expected.
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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 with the "priority" module parameter set
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(priority=1).
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1. If the kernel has not been booted with nmi_watchdog turned off then
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edit /boot/grub/menu.lst and place the nmi_watchdog=0 at the end of the
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currently booting kernel line.
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2. reboot the sever
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3. Once the system comes up perform a rmmod hpwdt
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4. insmod /lib/modules/`uname -r`/kernel/drivers/char/watchdog/hpwdt.ko priority=1
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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 HP BIOS).
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Below is a list of NMIs the HP BIOS understands along with the associated
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code (reason):
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No source found 00h
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Uncorrectable Memory Error 01h
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ASR NMI 1Bh
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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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(thomas.mingarelli@hp.com)
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