> > So either we severely constrain the kind of code that we permit to run
> > on other cores, or we enable the MMU and caches on each core as it
> > comes out of reset, as well as do any other CPU specific
> > initialization that we do for the primary core as well.
>
> The description for StartupAllAPs() has a note:
> It is the responsibility of the consumer of the
> EFI_MP_SERVICES_PROTOCOL.StartupAllAPs() to make sure that the nature
> of the code that is executed on the BSP and the dispatched APs is well
> controlled. The MP Services Protocol does not guarantee that the
> Procedure function is MP-safe. Hence, the tasks that can be run in
> parallel are limited to certain independent tasks and well-controlled
> exclusive code. EFI services and protocols may not be called by APs
> unless otherwise specified.
>
> So I think this is actually fine, implementation-wise. *Except* for
> the SwitchBSP function (where we're currently bailing out anyway).

Ok, so that doesn't look as bad as I thought. But we'll have to be
more strict than other arches: even EFI services and protocols that
are marked as safe for execution under this MP protocol are likely to
explode if they rely on CopyMem() or SetMem() for in/outputs that are
not a multiple of 8 bytes in case the platform uses the
BaseMemoryLibOptDxe flavour of this library, since it relies heavily
on deliberately misaligned loads and stores.