[src/trunk]: src/sys/arch/mips/mips Add a comment

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

details:   https://anonhg.NetBSD.org/src/rev/9803a970f1c7
branches:  trunk
changeset: 974708:9803a970f1c7
user:      skrll <skrll%NetBSD.org@localhost>
date:      Sun Aug 09 07:09:35 2020 +0000

description:
Add a comment

diffstat:

 sys/arch/mips/mips/vm_machdep.c |  8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diffs (29 lines):

diff -r 90681f756afd -r 9803a970f1c7 sys/arch/mips/mips/vm_machdep.c
--- a/sys/arch/mips/mips/vm_machdep.c   Sun Aug 09 07:08:29 2020 +0000
+++ b/sys/arch/mips/mips/vm_machdep.c   Sun Aug 09 07:09:35 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vm_machdep.c,v 1.160 2019/11/20 19:37:52 pgoyette Exp $        */
+/*     $NetBSD: vm_machdep.c,v 1.161 2020/08/09 07:09:35 skrll Exp $   */
 
 /*
  * Copyright (c) 1988 University of Utah.
@@ -39,7 +39,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vm_machdep.c,v 1.160 2019/11/20 19:37:52 pgoyette Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vm_machdep.c,v 1.161 2020/08/09 07:09:35 skrll Exp $");
 
 #include "opt_ddb.h"
 #include "opt_cputype.h"
@@ -120,6 +120,10 @@
                l2->l_md.md_upte[i] = 0;
        }
        if (!pmap_md_direct_mapped_vaddr_p(ua2)) {
+               /*
+                * UPAGES has to be 2 for 4KB PAGE_SIZE
+                * UPAGES has to be 1 for >= 8KB PAGE_SIZE
+                */
                CTASSERT((PGSHIFT == 12) == (UPAGES == 2));
                pt_entry_t * const pte = pmap_pte_lookup(pmap_kernel(), ua2);
                const uint32_t x = MIPS_HAS_R4K_MMU