Remove SFBUF_OPTIONAL_DIRECT_MAP and such hacks, replacing them across the

kernel by PHYS_TO_DMAP() as previously present on amd64, arm64, riscv, and
powerpc64. This introduces a new MI macro (PMAP_HAS_DMAP) that can be
evaluated at runtime to determine if the architecture has a direct map;
if it does not (or does) unconditionally and PMAP_HAS_DMAP is either 0 or
1, the compiler can remove the conditional logic.

As part of this, implement PHYS_TO_DMAP() on sparc64 and mips64, which had
similar things but spelled differently. 32-bit MIPS has a partial direct-map
that maps poorly to this concept and is unchanged.

Reviewed by:		kib
Suggestions from:	marius, alc, kib
Runtime tested on:	amd64, powerpc64, powerpc, mips64

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/amd64/include/vmparam.h b/sys/amd64/include/vmparam.h
index 6d63201c6581..bb8c3221eb6f 100644
--- a/sys/amd64/include/vmparam.h
+++ b/sys/amd64/include/vmparam.h
@@ -190,6 +190,7 @@
  * because the result is not actually accessed until later, but the early
  * vt fb startup needs to be reworked.
  */
+#define	PMAP_HAS_DMAP	1
 #define	PHYS_TO_DMAP(x)	({						\
 	KASSERT(dmaplimit == 0 || (x) < dmaplimit,			\
 	    ("physical address %#jx not covered by the DMAP",		\