[src/yamt-pagecache]: src/sys/uvm uvm_loanobj_read: try to avoid creating VAC...

[yamt <yamt%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/796975cece29
branches:  yamt-pagecache
changeset: 770852:796975cece29
user:      yamt <yamt%NetBSD.org@localhost>
date:      Wed Dec 28 13:24:19 2011 +0000

description:
uvm_loanobj_read: try to avoid creating VAC aliases if PMAP_PREFER is available

diffstat:

 sys/uvm/uvm_loan.c |  21 +++++++++++++++++++--
 1 files changed, 19 insertions(+), 2 deletions(-)

diffs (42 lines):

diff -r 54d895e4d65e -r 796975cece29 sys/uvm/uvm_loan.c
--- a/sys/uvm/uvm_loan.c        Wed Dec 28 13:22:47 2011 +0000
+++ b/sys/uvm/uvm_loan.c        Wed Dec 28 13:24:19 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_loan.c,v 1.81.2.7 2011/12/28 13:21:27 yamt Exp $   */
+/*     $NetBSD: uvm_loan.c,v 1.81.2.8 2011/12/28 13:24:19 yamt Exp $   */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -32,7 +32,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_loan.c,v 1.81.2.7 2011/12/28 13:21:27 yamt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_loan.c,v 1.81.2.8 2011/12/28 13:24:19 yamt Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -1394,6 +1394,23 @@
        if (npages > MAXPAGES) {
                return EINVAL;
        }
+#if defined(PMAP_PREFER)
+       /*
+        * avoid creating VAC aliases.
+        */
+       {
+               const vaddr_t origva = va;
+
+               PMAP_PREFER(off, &va, len, 0);
+               if (va != origva) {
+                       /*
+                        * pmap's suggestion was different from the requested
+                        * address.  punt.
+                        */
+                       return EINVAL;
+               }
+       }
+#endif /* defined(PMAP_PREFER) */
 retry:
        vm_map_lock_read(map);
        if (!uvm_map_lookup_entry(map, va, &entry)) {