We can now properly initialize all processors without
crashing by sending SMP IPI messages to synchronize memory
between processors.
We now initialize the APs once we have the scheduler running.
This is so that we can process IPI messages from the other
cores.
Also rework interrupt handling a bit so that it's more of a
1:1 mapping. We need to allocate non-sharable interrupts for
IPIs.
This also fixes the occasional hang/crash because all
CPUs now synchronize memory with each other.
Add a MappedROM::find_chunk_starting_with() helper since that's a very
common usage pattern in clients of this code.
Also convert MultiProcessorParser from a persistent singleton object
to a temporary object constructed via a failable factory function.
This patch adds a MappedROM abstraction to the Kernel VM subsystem.
It's basically the read-only byte buffer equivalent of a TypedMapping.
We use this in the ACPI and MP table parsers to scan for interesting
stuff in low memory instead of doing a bunch of address arithmetic.
This was supposed to be the foundation for some kind of pre-kernel
environment, but nobody is working on it right now, so let's move
everything back into the kernel and remove all the confusion.
