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diff --git a/Documentation/watchdog/hpwdt.txt b/Documentation/watchdog/hpwdt.txt new file mode 100644 index 000000000..6d866c537 --- /dev/null +++ b/Documentation/watchdog/hpwdt.txt @@ -0,0 +1,97 @@ +Last reviewed: 05/20/2016 + + HPE iLO NMI Watchdog Driver + NMI sourcing for iLO based ProLiant Servers + Documentation and Driver by + Thomas Mingarelli + + 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. + All references to iLO in this document imply it also works on iLO2 and all + subsequent generations. + + Watchdog functionality is enabled like any other common watchdog driver. That + is, an application needs to be started that kicks off the watchdog timer. A + basic application exists in tools/testing/selftests/watchdog/ named + watchdog-test.c. Simply compile the C file and kick it off. If the system + gets into a bad state and hangs, the HPE ProLiant iLO timer register will + 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: + + 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 + 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 + to "Y", then there is no way of disabling the watchdog once + it has been started. + + NOTE: More information about watchdog drivers in general, including the ioctl + 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 + + Front Side Bus NMI 2Dh + + PCI Express Error 2Fh + + DMA controller NMI 30h + + Hypertransport/CSI Error 31h + + + + -- Tom Mingarelli |