Add arch-specific macro SFBUF_PHYS_DMAP(), which should translate the

physical address of the page to direct map address, in case
SFBUF_OPTIONAL_DIRECT_MAP returns true.  The case of PowerPC AIM
64bit, where the page physical address is identical to the direct map
address, is accidental.

Reviewed by:	alc
Sponsored by:	The FreeBSD Foundation

sys/powerpc/include/vmparam.h

@@ -210,5 +210,6 @@ struct pmap_physseg {
 #define	SFBUF
 #define	SFBUF_NOMD
 #define	SFBUF_OPTIONAL_DIRECT_MAP	hw_direct_map
+#define	SFBUF_PHYS_DMAP(x)		(x)
  
 #endif /* _MACHINE_VMPARAM_H_ */

sys/sys/sf_buf.h

@@ -113,7 +113,7 @@ sf_buf_kva(struct sf_buf *sf)
 {
 #ifdef SFBUF_OPTIONAL_DIRECT_MAP
 	if (SFBUF_OPTIONAL_DIRECT_MAP)
-		return (VM_PAGE_TO_PHYS((vm_page_t)sf));
+		return (SFBUF_PHYS_DMAP(VM_PAGE_TO_PHYS((vm_page_t)sf)));
 #endif
 
         return (sf->kva);