Re: [PATCH 1/4] powerpc/powernv: handle the platform error reboot in ppc_md.restart

[Nicholas Piggin <npiggin@gmail.com>]

On Wed,  5 Jul 2017 14:04:19 +1000
Nicholas Piggin <npiggin@gmail.com> wrote:

> Unrecovered MCE and HMI errors are sent through a special restart
> OPAL call to log the platform error. The downside is that they don't
> go through normal crash paths, so they don't give much information
> to the Linux console.
> 
> Change this by allowing them to set an error which then causes the
> normal restart handler to use the platform error call. Have MCE and HMI
> handlers set this and then use the normal panic path for unrecoverable
> cases.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---

This patch is a bit clunky, setting this global variable. But it's
difficult to get this through the normal crash/panic paths by any
other way that I've found.

A concern is that we would like to add the opal log as early as
possible, but also print some information to the Linux console. This
goes against a competing concern that the more we do before logging
and xstop, the larger window something might go wrong.

So I would like to be able to cause opal to log a platform error
ASAP in the machine check handler, but then do some Linux crash
dumping before xstopping. That would require a new opal logging API
or convention though. So maybe this is an improvement (which also
allows patch 2 to be implemented more easily).

Anyway, discussion and criticism welcome.


Thanks,
Nick