* [RFC] NMI: Generic per-code NMI handler (panic/kdump)
@ 2017-05-06 23:05 Adrien Mahieux
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From: Adrien Mahieux @ 2017-05-06 23:05 UTC (permalink / raw)
To: linux-kernel
Hello,
I'm new to the LKML, so should I make mistakes, please tell me along with
the correct way to do (or doc I've read but forgotten).
I've written a small module to manage NMI events based on their code, so a
sysadmin can drop them (avoid console messages) or panic the kernel (kdump).
https://github.com/Saruspete/nmimgr/blob/master/nmimgr.c
So far, working as expected in massive prod, with different kernels.
As a newbie, I've got some questions I didn't found response in the docs:
- My code is supporting multiple versions with KERNEL_VERSION macro, but I
read it's not recommanded and should just be compiling against masters head.
May I leave this as is to ease the distributions' maintainers work ?
- In what subsystem/file should it go ?
arch/x86/kernel/nmi.c (but should be for all archs)
kernel/watchdog.c (but not a watchdog)
drivers/char/ipmi (but not an IPMI nor a driver)
- How to know where to place its Kconfig menus ? It's easy for drivers, but
what about this one ?
- If someone has time to review the code and point me cases I didn't think
of, would be happy to fix them.
Here are some real-life usage of this module:
- When my servers are frozen, I generate an NMI from IPMI "power diag". But the
event code changes between each hardware vendor (even different gen of the
same vendor) and I have some specific hardware (like fpgas) that generates
NMI as well, or near-dead parts that generates some too so I can't use
*nmi_panic sysctls.
- When using hpwdt module, it registers an equivalent of panic upon any nmi
event. So I still want the watchdog, but only upon ILO and ASR NMIs, not
all others.
- During a kdump, some servers may take a lot of time to dump memory. If the
server receives another NMI, it'll reboot and loose the current dump. By
dropping all NMIs, it acts as a fence during the kdump.
To help the usage, I've added a "setup.sh" in the repo to build and configure
the kmod with the NMI events matching the current hardware (HP, Dell, IBM,
VirtualBox...).
Thanks for your guidance.
Adrien.
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