MFC r273701, r274556

  By the time that pmap_init() runs, vm_phys_segs[] has been initialized.
  Obtaining the end of memory address from vm_phys_segs[] is a little
  easier than obtaining it from phys_avail[].

  Enable the use of VM_PHYSSEG_SPARSE on amd64 and i386, making it the
  default on i386 PAE.  (The use of VM_PHYSSEG_SPARSE on i386 PAE saves
  us some precious kernel virtual address space that would have been
  wasted on unused vm_page structures.)

1 files changed, 11 insertions, 2 deletions

diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index 6d894f3..fe3850f 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -130,6 +130,7 @@ __FBSDID("$FreeBSD$");
 #include <vm/vm_extern.h>
 #include <vm/vm_pageout.h>
 #include <vm/vm_pager.h>
+#include <vm/vm_phys.h>
 #include <vm/vm_radix.h>
 #include <vm/vm_reserv.h>
 #include <vm/uma.h>
@@ -836,6 +837,15 @@ pmap_bootstrap(vm_paddr_t *firstaddr)
 	 */
 	create_pagetables(firstaddr);
 
+	/*
+	 * Add a physical memory segment (vm_phys_seg) corresponding to the
+	 * preallocated kernel page table pages so that vm_page structures
+	 * representing these pages will be created.  The vm_page structures
+	 * are required for promotion of the corresponding kernel virtual
+	 * addresses to superpage mappings.
+	 */
+	vm_phys_add_seg(KPTphys, KPTphys + ptoa(nkpt));
+
 	virtual_avail = (vm_offset_t) KERNBASE + *firstaddr;
 	virtual_avail = pmap_kmem_choose(virtual_avail);
 
@@ -1060,8 +1070,7 @@ pmap_init(void)
 	/*
 	 * Calculate the size of the pv head table for superpages.
 	 */
-	for (i = 0; phys_avail[i + 1]; i += 2);
-	pv_npg = round_2mpage(phys_avail[(i - 2) + 1]) / NBPDR;
+	pv_npg = howmany(vm_phys_segs[vm_phys_nsegs - 1].end, NBPDR);
 
 	/*
 	 * Allocate memory for the pv head table for superpages.