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Make refs to selftests files valid including: - watchdog-test.c - dnotify_test.c Signed-off-by: Tom Saeger <tom.saeger@oracle.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
98 lines
3.8 KiB
Plaintext
98 lines
3.8 KiB
Plaintext
Last reviewed: 05/20/2016
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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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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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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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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 tools/testing/selftests/watchdog/ named
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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 HPE ProLiant iLO 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 three (3) 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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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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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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to "Y", then there is no way of disabling the watchdog once
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it has been started.
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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 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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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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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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Below is a list of NMIs the HPE 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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