More on kexec/purgatory handover

[Jan Beulich]

>>> On 13.05.15 at 07:26, <ebiederm at xmission.com> wrote:
> The low 640k was weird.   We copied it off in purgatory so that it could
> be capture in a dump.  The linux kernel itself winds up using that
> memory fundamentally because to fire up subsequent processors you have
> to have memory in the low 640k as processors start in real-mode and
> the startup IPI only takes an address in the low 1M.  I also remember
> things with interrupt descriptor tables.

Right, but the point to clarify is whether it is reasonable for the
purgatory and/or new kernel to expect the old kernel to set up
mappings for special regions like this one. As said before - I don't
think this should be done; the old (possibly half broken) kernel
shouldn't be forced to do any more than the absolute minimum
amount of work to be able to transfer control.

Jan