[OpenPower-Firmware] Generate a dump of the Linux kernel on host OS (P8)

[Stewart Smith]

Artem Senichev <artemsen at gmail.com> writes:
> I need the ability to generate a dump of the Linux kernel on host OS
> using a command from BMC.
>
> As far as I know, the dump is generated as part of NMI handler in the
> Linux Kernel.
> The NMI handler is configured at startup and depends on
> OPAL_SIGNAL_SYSTEM_RESET support flag:
> https://github.com/torvalds/linux/blob/master/arch/powerpc/platforms/powernv/smp.c#L391
>
> Currently, only P9 supports the system reset signal feature:
> https://github.com/open-power/skiboot/blob/master/core/direct-controls.c#L810
> But function p9_sreset_cpu() uses calls with branches depending on CPU
> gen, for example dctl_sreset() calls p8_sreset_thread() or
> p8_sreset_thread():
> https://github.com/open-power/skiboot/blob/master/core/direct-controls.c#L636
>
> So, I have a couple of questions:
> 1. Is there exist an IPMI command which I can send to the OPAL to
> generate the dump?

I don't think we have the IPMI NMI command hooked up to anything
currently, and I haven't really thought at all about how we should hook
that up.

> 2. Is it possible to implement P8 support for OPAL_SIGNAL_SYSTEM_RESET
> feature?

Alistair has a patch from a while ago that implements it using
instruction ramming: https://patchwork.ozlabs.org/patch/694794/

This uses some scom register writes to force a cpu core to execute
instructions we tell it to (which is basically jump to 0x100).

This patch will need a bit of cleanup/rebase to current skiboot, which
you could either give a go or we bribe Alistair to do it with a few
beers :)

-- 
Stewart Smith
OPAL Architect, IBM.