to make it possible to mark the bootscreen framebuffer
as write combining in early initialization, mtrr() is
changed not not to error() but to return an error string.
as bootscreen() is used before multiprocessor initialization,
we have to synchronize the mtrr's for every processor as
it comes online. for this, a new mtrrsync() function is
provided that is called from cpuidentify() if mtrr support
is indicated.
the boot processor runs mtrrsync() which snarfs the
registers. later, mtrrsync() is run again from the
application processors which apply the values from the
boot processor.
checkmtrr() from mp.c was removed as its task is also
done by mtrrsync() now.
as we do system reset and reboot only from boot processor cpu0 now,
theres no need for active.rebooting conditional variable.
mpshutdown() will unconditionally park application processors and
and cpu0 boots the new kernel or calls mpshutdown() causing system
reset.
in vmware, mpshutdown() used to hang in i8042reset() when not
called from the boot processor, so instead of reseting from first
cpu that acquires the shutdown lock, we park all application
processors and let the boot processor do the reset.
we used to only test the checksum of the PCMP structure referenced by
the _MP_ without checking _MP_ itself. now fixed.
geoff added some coherence() calls and comments in the mpstartup and
apic code which seems to be a good idea.
