Page Attribute Tables (PAT) support for x86.

PAT allows setting per-mapping cachability bits. Our main interest in it
for write combining mappings so we do not have to rely so heaviliy on
mtrrs (which are stupidly set up on more and more machines). MD flags to
pmap allow setting these bits (which bus_space now uses for PREFETCHABLE
maps), if a vm page has a bit set, then we will use WC for all mappings
of a page (used for userland mappings). We also check for known errata
and fall back to UC- mappings in that case.

comments from kettenis@, tedu@ and william@. kettenis@, tedu@ ok.

1 files changed, 4 insertions, 2 deletions

diff --git a/sys/arch/i386/include/pmap.h b/sys/arch/i386/include/pmap.h
index bd62351d892..393938975ac 100644
--- a/sys/arch/i386/include/pmap.h
+++ b/sys/arch/i386/include/pmap.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pmap.h,v 1.54 2009/12/09 14:31:57 oga Exp $	*/
+/*	$OpenBSD: pmap.h,v 1.55 2010/05/08 16:54:08 oga Exp $	*/
 /*	$NetBSD: pmap.h,v 1.44 2000/04/24 17:18:18 thorpej Exp $	*/
 
 /*
@@ -298,12 +298,14 @@ struct pv_entry {			/* locked by its list's pvh_lock */
 /* to get just the pa from params to pmap_enter */
 #define PMAP_PA_MASK	~((paddr_t)PAGE_MASK)
 #define	PMAP_NOCACHE	0x1		/* map uncached */
+#define	PMAP_WC		0x2		/* map write combining. */
 
 /*
  * We keep mod/ref flags in struct vm_page->pg_flags.
  */
-#define PG_PMAP_MOD	PG_PMAP0
+#define	PG_PMAP_MOD	PG_PMAP0
 #define	PG_PMAP_REF	PG_PMAP1
+#define	PG_PMAP_WC	PG_PMAP2
 
 /*
  * pv_entrys are dynamically allocated in chunks from a single page.