modifying the kernel pdp (CPU0PDP) hangs vmware. so
we initialize the pdp with KZERO and KZERO+1GB map
in l.s and never change it. (except when removing
the zero double map which seems to work).
VMAP has its own pdp now allowing to map 512GB of
physical address space. this simplifies the code
a bit and gives nice virtual addresses.
on intel processors, a general protection exception is fired if a non-canonical address is loaded into PC during SYSRET. this will cause the kernel to panic.
see http://www.kb.cert.org/vuls/id/649219 and the intel software developer manual for more information.
kmapindex has to be per process, not per mach, as the process
can be switched to another processor while the mapping is
established.
to bootstrap the first process, we have to temporarily set up
so the kmap MMU's can be attached to the process. previously
we assumed that the first two pages for the initial process
where below 2GB and could be accessed with KADDR() directly.
with 16GB machine, all the 2GB above KZERO are dedicated to
the kernel so the user pages returned by newpage() need to
be mapped.
we have to keep kmap page tables in ther own list
because user tables are subject to (virtual) tlb flushing.
we never free kmap page tables except in mmurelease()
where we just link the kmap mmu list in front of the user
mmus and call mmufree() which will free all the mmu's
of the process.
