[src/trunk]: src/sys/arch/amd64/stand/prekern Descend the page tree from L4 t...

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

details:   https://anonhg.NetBSD.org/src/rev/dfe1eacbe60f
branches:  trunk
changeset: 827115:dfe1eacbe60f
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sun Oct 15 06:37:32 2017 +0000

description:
Descend the page tree from L4 to L1, instead of allocating a separate
branch and linking it at the end. This way we don't need to allocate VA
from the (tiny) prekern map.

diffstat:

 sys/arch/amd64/stand/prekern/mm.c |  99 +++++++++++++++-----------------------
 1 files changed, 40 insertions(+), 59 deletions(-)

diffs (161 lines):

diff -r 748a0e5b982b -r dfe1eacbe60f sys/arch/amd64/stand/prekern/mm.c
--- a/sys/arch/amd64/stand/prekern/mm.c Sun Oct 15 06:15:37 2017 +0000
+++ b/sys/arch/amd64/stand/prekern/mm.c Sun Oct 15 06:37:32 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mm.c,v 1.1 2017/10/10 09:29:14 maxv Exp $      */
+/*     $NetBSD: mm.c,v 1.2 2017/10/15 06:37:32 maxv Exp $      */
 
 /*
  * Copyright (c) 2017 The NetBSD Foundation, Inc. All rights reserved.
@@ -41,8 +41,7 @@
 vaddr_t iom_base;
 
 paddr_t pa_avail = 0;
-static vaddr_t va_avail = (PREKERNBASE + NKL2_KIMG_ENTRIES * NBPD_L2);
-static vaddr_t va_end = (PREKERNBASE + (NKL2_KIMG_ENTRIES + 1) * NBPD_L2);
+static const vaddr_t tmpva = (PREKERNBASE + NKL2_KIMG_ENTRIES * NBPD_L2);
 
 void
 mm_init(paddr_t first_pa)
@@ -50,25 +49,6 @@
        pa_avail = first_pa;
 }
 
-static paddr_t
-mm_palloc(size_t npages)
-{
-       paddr_t pa = pa_avail;
-       pa_avail += npages * PAGE_SIZE;
-       return pa;
-}
-
-static vaddr_t
-mm_valloc(size_t npages)
-{
-       vaddr_t va = va_avail;
-       va_avail += npages * PAGE_SIZE;
-       if (va_avail > va_end) {
-               fatal("mm_valloc: no VA left");
-       }
-       return va;
-}
-
 static void
 mm_enter_pa(paddr_t pa, vaddr_t va, pte_prot_t prot)
 {
@@ -81,6 +61,27 @@
        asm volatile("invlpg (%0)" ::"r" (va) : "memory");
 }
 
+static paddr_t
+mm_palloc(size_t npages)
+{
+       paddr_t pa;
+       size_t i;
+
+       /* Allocate the physical pages */
+       pa = pa_avail;
+       pa_avail += npages * PAGE_SIZE;
+
+       /* Zero them out */
+       for (i = 0; i < npages; i++) {
+               mm_enter_pa(pa + i * PAGE_SIZE, tmpva,
+                   MM_PROT_READ|MM_PROT_WRITE);
+               mm_flush_va(tmpva);
+               memset((void *)tmpva, 0, PAGE_SIZE);
+       }
+
+       return pa;
+}
+
 paddr_t
 mm_vatopa(vaddr_t va)
 {
@@ -106,13 +107,11 @@
 }
 
 static void
-mm_map_va(vaddr_t startva, vaddr_t endva)
+mm_map_tree(vaddr_t startva, vaddr_t endva)
 {
-       size_t i, idx, size, nL4e, nL3e, nL2e;
+       size_t i, size, nL4e, nL3e, nL2e;
        size_t L4e_idx, L3e_idx, L2e_idx;
-       vaddr_t L3page_va, L2page_va;
        paddr_t L3page_pa, L2page_pa, L1page_pa;
-       pd_entry_t *pdir;
 
        /*
         * Initialize constants.
@@ -122,48 +121,30 @@
        nL3e = roundup(size, NBPD_L3) / NBPD_L3;
        nL2e = roundup(size, NBPD_L2) / NBPD_L2;
        L4e_idx = pl4_i(startva);
-       L3e_idx = pl3_i(startva % NBPD_L4);
-       L2e_idx = pl2_i(startva % NBPD_L3);
+       L3e_idx = pl3_i(startva);
+       L2e_idx = pl2_i(startva);
+
+       ASSERT(nL4e == 1);
+       ASSERT(L4e_idx == 511);
 
        /*
-        * Map the sub-tree itself.
+        * Allocate the physical pages.
         */
-       L3page_va = mm_valloc(nL4e);
        L3page_pa = mm_palloc(nL4e);
-       L2page_va = mm_valloc(nL3e);
        L2page_pa = mm_palloc(nL3e);
-
        L1page_pa = mm_palloc(nL2e);
 
-       for (i = 0; i < nL4e; i++) {
-               mm_enter_pa(L3page_pa + i * PAGE_SIZE,
-                   L3page_va + i * PAGE_SIZE, MM_PROT_READ|MM_PROT_WRITE);
-               memset((void *)(L3page_va + i * PAGE_SIZE), 0, PAGE_SIZE);
-       }
-
-       for (i = 0; i < nL3e; i++) {
-               mm_enter_pa(L2page_pa + i * PAGE_SIZE,
-                   L2page_va + i * PAGE_SIZE, MM_PROT_READ|MM_PROT_WRITE);
-               memset((void *)(L2page_va + i * PAGE_SIZE), 0, PAGE_SIZE);
-       }
-
        /*
-        * Now link the levels together.
-        */
-       pdir = (pt_entry_t *)L3page_va;
-       for (i = 0, idx = L3e_idx; i < nL3e; i++, idx++) {
-               pdir[idx] = (L2page_pa + i * PAGE_SIZE) | PG_V | PG_RW;
-       }
-
-       pdir = (pt_entry_t *)L2page_va;
-       for (i = 0, idx = L2e_idx; i < nL2e; i++, idx++) {
-               pdir[idx] = (L1page_pa + i * PAGE_SIZE) | PG_V | PG_RW;
-       }
-
-       /*
-        * Finally, link the sub-tree into the tree.
+        * Build the branch in the page tree. We link the levels together,
+        * from L4 to L1.
         */
        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;
+       }
+       for (i = 0; i < nL2e; i++) {
+               L2_BASE[L2e_idx+i] = (L1page_pa + i * PAGE_SIZE) | PG_V | PG_RW;
+       }
 }
 
 /*
@@ -185,7 +166,7 @@
        randva = rounddown(KASLR_WINDOW_BASE + rnd % (KASLR_WINDOW_SIZE - size),
            PAGE_SIZE);
 
-       mm_map_va(randva, randva + size);
+       mm_map_tree(randva, randva + size);
 
        return randva;
 }