pc, pc64: make mtrr() callable from interrupt context and before mpinit

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.

1 files changed, 2 insertions, 1 deletions

diff --git a/sys/src/9/pc/fns.h b/sys/src/9/pc/fns.h
index 99fa4b671..8ecaa0f7d 100644
--- a/sys/src/9/pc/fns.h
+++ b/sys/src/9/pc/fns.h
@@ -111,9 +111,10 @@ void	mfence(void);
 #define mmuflushtlb(pdb) putcr3(pdb)
 void	mmuinit(void);
 ulong*	mmuwalk(ulong*, ulong, int, int);
-int	mtrr(uvlong, uvlong, char *);
+char*	mtrr(uvlong, uvlong, char *);
 void	mtrrclock(void);
 int	mtrrprint(char *, long);
+void	mtrrsync(void);
 uchar	nvramread(int);
 void	nvramwrite(int, uchar);
 void	outb(int, int);