dead hvc_console with kdump kernel

[Benjamin Herrenschmidt]

> The problem is this is counter to the goal of kdump trusting anything
> in the old kernel when going to the new kernel.  In fact this would be
> walking dynamic data structures.

Well, I suppose you could just end EOIs to the APICs for every
interrupts, won't harm... but you still need the list of APICs... You
should also mask on them

> Also, does it cover us on interrupts that are sent against a cpu that
> we choose not to online in the second kernel?  Or interrupts that are
> sent after the loop (devices are not stopped at that point)
> 
> Hence the asked question, does the reset cover us?

Dunno. Definitely doesn't cover APICs. You really need to disable all
IRQ source on the MPIC, I wouldn't trust reset to be implemented
properly.

> This can now be tested expermentially with Michael's debugfs
> patch harness.
> 
> milton