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, 13 insertions, 2 deletions

diff --git a/sys/i386/i386/pmap.c b/sys/i386/i386/pmap.c
index c9bff6b..3bd44d9 100644
--- a/sys/i386/i386/pmap.c
+++ b/sys/i386/i386/pmap.c
@@ -133,6 +133,7 @@ __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>
@@ -374,6 +375,15 @@ pmap_bootstrap(vm_paddr_t firstaddr)
 	int i;
 
 	/*
+	 * 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));
+
+	/*
 	 * Initialize the first available kernel virtual address.  However,
 	 * using "firstaddr" may waste a few pages of the kernel virtual
 	 * address space, because locore may not have mapped every physical
@@ -778,9 +788,10 @@ pmap_init(void)
 
 	/*
 	 * Calculate the size of the pv head table for superpages.
+	 * Handle the possibility that "vm_phys_segs[...].end" is zero.
 	 */
-	for (i = 0; phys_avail[i + 1]; i += 2);
-	pv_npg = round_4mpage(phys_avail[(i - 2) + 1]) / NBPDR;
+	pv_npg = trunc_4mpage(vm_phys_segs[vm_phys_nsegs - 1].end -
+	    PAGE_SIZE) / NBPDR + 1;
 
 	/*
 	 * Allocate memory for the pv head table for superpages.