Enable high memory

* i386/i386at/biosmem.c (biosmem_setup): Load the HIGHMEM segment if
present.
(biosmem_free_usable): Report high memory as usable.
* vm/vm_page.c (vm_page_boot_table_size, vm_page_table_size,
vm_page_mem_size, vm_page_mem_free): Scan all segments.
* vm/vm_resident.c (vm_page_grab): Describe allocation strategy
with regard to the HIGHMEM segment.

3 files changed, 12 insertions, 22 deletions

diff --git a/i386/i386at/biosmem.c b/i386/i386at/biosmem.c
index 62be567c..a1040207 100644
--- a/i386/i386at/biosmem.c
+++ b/i386/i386at/biosmem.c
@@ -903,9 +903,7 @@ biosmem_setup(void)
             break;
 
         seg = &biosmem_segments[i];
-
-        /* XXX Limit to directmap until highmem is supported */
-        biosmem_load_segment(seg, VM_PAGE_DIRECTMAP_LIMIT);
+        biosmem_load_segment(seg, VM_PAGE_HIGHMEM_LIMIT);
     }
 }
 
@@ -986,9 +984,8 @@ biosmem_free_usable(void)
 
         end = vm_page_trunc(entry->base_addr + entry->length);
 
-        /* XXX Limit to directmap until highmem is supported */
-        if (end > VM_PAGE_DIRECTMAP_LIMIT) {
-            end = VM_PAGE_DIRECTMAP_LIMIT;
+        if (end > VM_PAGE_HIGHMEM_LIMIT) {
+            end = VM_PAGE_HIGHMEM_LIMIT;
         }
 
         if (start < BIOSMEM_BASE)
diff --git a/vm/vm_page.c b/vm/vm_page.c
index 4c11ea7a..2a9f27b2 100644
--- a/vm/vm_page.c
+++ b/vm/vm_page.c
@@ -1620,10 +1620,6 @@ vm_page_boot_table_size(void)
     nr_pages = 0;
 
     for (i = 0; i < vm_page_segs_size; i++) {
-        /* XXX */
-        if (i > VM_PAGE_SEG_DIRECTMAP)
-            continue;
-
         nr_pages += vm_page_atop(vm_page_boot_seg_size(&vm_page_boot_segs[i]));
     }
 
@@ -1643,10 +1639,6 @@ vm_page_table_size(void)
     nr_pages = 0;
 
     for (i = 0; i < vm_page_segs_size; i++) {
-        /* XXX */
-        if (i > VM_PAGE_SEG_DIRECTMAP)
-            continue;
-
         nr_pages += vm_page_atop(vm_page_seg_size(&vm_page_segs[i]));
     }
 
@@ -1684,10 +1676,6 @@ vm_page_mem_size(void)
     total = 0;
 
     for (i = 0; i < vm_page_segs_size; i++) {
-        /* XXX */
-        if (i > VM_PAGE_SEG_DIRECTMAP)
-            continue;
-
         total += vm_page_seg_size(&vm_page_segs[i]);
     }
 
@@ -1703,10 +1691,6 @@ vm_page_mem_free(void)
     total = 0;
 
     for (i = 0; i < vm_page_segs_size; i++) {
-        /* XXX */
-        if (i >  VM_PAGE_SEG_DIRECTMAP)
-            continue;
-
         total += vm_page_segs[i].nr_free_pages;
     }
 
diff --git a/vm/vm_resident.c b/vm/vm_resident.c
index e276fe68..e3e34dc3 100644
--- a/vm/vm_resident.c
+++ b/vm/vm_resident.c
@@ -771,6 +771,15 @@ vm_page_t vm_page_grab(void)
 
 	simple_lock(&vm_page_queue_free_lock);
 
+	/*
+	 * XXX Mach has many modules that merely assume memory is
+	 * directly mapped in kernel space. Instead of updating all
+	 * users, we assume those which need specific physical memory
+	 * properties will wire down their pages, either because
+	 * they can't be paged (not part of an object), or with
+	 * explicit VM calls. The strategy is then to let memory
+	 * pressure balance the physical segments with pageable pages.
+	 */
 	mem = vm_page_alloc_pa(0, VM_PAGE_SEL_DIRECTMAP, VM_PT_KERNEL);
 
 	if (mem == NULL) {