[Skiboot] [PATCH v2 1/2] mpipl: Delay MPIPL registration until OPAL init is complete

[Oliver O'Halloran]

On Wed, Jun 17, 2020 at 5:16 PM Vasant Hegde
<hegdevasant at linux.vnet.ibm.com> wrote:
>
> If OPAL boot fails after MPIPL init (opal_mpipl_init()) then we call MPIPL
> boot instead of reboot. BMC is not aware of MPIPL. Hence it may result in
> continuous MPIPL loop (boot -> crash -> MPIPL -> boot).
>
> If OPAL boot fails (before loading kernel) then its better to call reboot.
> So that BMC can detect `n` number of boot failures (generally n = 3) and
> stop booting. That way we can avoid continuous loop.
>
> This patch moves MPIPL init to the end of init process (just before starting
> kernel). So that if we fail to boot OPAL we call normal reboot.
>
> Also this patch introduces new function to detect MPIPL is enabled or not
> (is_mpipl_enabled()). And in assert() path we check for this function
> instead of `dump` DT node. So that it will make sure we will not call
> MPIPL until opal_mpipl_init is complete.

Why do we even allow repeated MPIPLs? Just seems like a good way to
get stuck in a boot loop.

This patch sorta helps, but we've got the same problem if we happen to
hit a crash while petitboot is running. Maybe we should only MPIPL if
the host kernel explicitly requests one rather than hacking it into
the termination path like we're doing now.