[src/trunk]: src/sys/arch/amd64/stand/prekern If a branch is already there, u...

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

details:   https://anonhg.NetBSD.org/src/rev/74ac82344088
branches:  trunk
changeset: 356877:74ac82344088
user:      maxv <maxv%NetBSD.org@localhost>
date:      Wed Oct 18 17:12:42 2017 +0000

description:
If a branch is already there, use it and don't create a new one. This way
we can call mm_map_tree twice with neighboring regions.

diffstat:

 sys/arch/amd64/stand/prekern/mm.c |  57 +++++++++++++++++++++++---------------
 1 files changed, 35 insertions(+), 22 deletions(-)

diffs (90 lines):

diff -r 3834a9ee6562 -r 74ac82344088 sys/arch/amd64/stand/prekern/mm.c
--- a/sys/arch/amd64/stand/prekern/mm.c Wed Oct 18 16:29:56 2017 +0000
+++ b/sys/arch/amd64/stand/prekern/mm.c Wed Oct 18 17:12:42 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mm.c,v 1.2 2017/10/15 06:37:32 maxv Exp $      */
+/*     $NetBSD: mm.c,v 1.3 2017/10/18 17:12:42 maxv Exp $      */
 
 /*
  * Copyright (c) 2017 The NetBSD Foundation, Inc. All rights reserved.
@@ -82,6 +82,12 @@
        return pa;
 }
 
+static bool
+mm_pte_is_valid(pt_entry_t pte)
+{
+       return ((pte & PG_V) != 0);
+}
+
 paddr_t
 mm_vatopa(vaddr_t va)
 {
@@ -111,39 +117,46 @@
 {
        size_t i, size, nL4e, nL3e, nL2e;
        size_t L4e_idx, L3e_idx, L2e_idx;
-       paddr_t L3page_pa, L2page_pa, L1page_pa;
+       paddr_t pa;
+
+       size = endva - startva;
 
        /*
-        * Initialize constants.
+        * Build L4.
         */
-       size = endva - startva;
+       L4e_idx = pl4_i(startva);
        nL4e = roundup(size, NBPD_L4) / NBPD_L4;
-       nL3e = roundup(size, NBPD_L3) / NBPD_L3;
-       nL2e = roundup(size, NBPD_L2) / NBPD_L2;
-       L4e_idx = pl4_i(startva);
-       L3e_idx = pl3_i(startva);
-       L2e_idx = pl2_i(startva);
-
+       ASSERT(L4e_idx == 511);
        ASSERT(nL4e == 1);
-       ASSERT(L4e_idx == 511);
+       if (!mm_pte_is_valid(L4_BASE[L4e_idx])) {
+               pa = mm_palloc(1);
+               L4_BASE[L4e_idx] = pa | PG_V | PG_RW;
+       }
 
        /*
-        * Allocate the physical pages.
+        * Build L3.
         */
-       L3page_pa = mm_palloc(nL4e);
-       L2page_pa = mm_palloc(nL3e);
-       L1page_pa = mm_palloc(nL2e);
+       L3e_idx = pl3_i(startva);
+       nL3e = roundup(size, NBPD_L3) / NBPD_L3;
+       for (i = 0; i < nL3e; i++) {
+               if (mm_pte_is_valid(L3_BASE[L3e_idx+i])) {
+                       continue;
+               }
+               pa = mm_palloc(1);
+               L3_BASE[L3e_idx+i] = pa | PG_V | PG_RW;
+       }
 
        /*
-        * Build the branch in the page tree. We link the levels together,
-        * from L4 to L1.
+        * Build L2.
         */
-       L4_BASE[L4e_idx] = L3page_pa | PG_V | PG_RW;
-       for (i = 0; i < nL3e; i++) {
-               L3_BASE[L3e_idx+i] = (L2page_pa + i * PAGE_SIZE) | PG_V | PG_RW;
-       }
+       L2e_idx = pl2_i(startva);
+       nL2e = roundup(size, NBPD_L2) / NBPD_L2;
        for (i = 0; i < nL2e; i++) {
-               L2_BASE[L2e_idx+i] = (L1page_pa + i * PAGE_SIZE) | PG_V | PG_RW;
+               if (mm_pte_is_valid(L2_BASE[L2e_idx+i])) {
+                       continue;
+               }
+               pa = mm_palloc(1);
+               L2_BASE[L2e_idx+i] = pa | PG_V | PG_RW;
        }
 }