expanding amd64 past the 1TB limit

[Chris Torek]

I went ahead and implemented the "ndmpdpphys" change I
had thought about.  Here's that patch by itself.

At this point it might be reasonable to use the patch
without the AMD64_HUGE option, just increasing the KVM
area, as the direct map no longer consumes extra pages.

(There's a glitch in the comment in the original patch,
I'll fix that if/when there's any agreement on whether
it gets applied in some form :-) )

Chris

diff --git a/amd64/amd64/pmap.c b/amd64/amd64/pmap.c
index acf5af2..f1ed8b6 100644
--- a/amd64/amd64/pmap.c
+++ b/amd64/amd64/pmap.c
@@ -232,6 +232,7 @@ u_int64_t		KPML4phys;	/* phys addr of kernel level 4 */
 
 static u_int64_t	DMPDphys;	/* phys addr of direct mapped level 2 */
 static u_int64_t	DMPDPphys;	/* phys addr of direct mapped level 3 */
+static int		ndmpdpphys;	/* number of DMPDPphys pages */
 
 static struct rwlock_padalign pvh_global_lock;
 
@@ -543,7 +544,18 @@ create_pagetables(vm_paddr_t *firstaddr)
 	ndmpdp = (ptoa(Maxmem) + NBPDP - 1) >> PDPSHIFT;
 	if (ndmpdp < 4)		/* Minimum 4GB of dirmap */
 		ndmpdp = 4;
-	DMPDPphys = allocpages(firstaddr, NDMPML4E);
+	ndmpdpphys = howmany(ndmpdp, NPML4EPG);
+	if (ndmpdpphys > NDMPML4E) {
+		/*
+		 * Each NDMPML4E allows 512 GB, so limit to that,
+		 * and then readjust ndmpdp and ndmpdpphys.
+		 */
+		printf("NDMPML4E limits system to %d GB\n", NDMPML4E * 512);
+		Maxmem = atop(NDMPML4E * NBPML4);
+		ndmpdpphys = NDMPML4E;
+		ndmpdp = NDMPML4E * NPDEPG;
+	}
+	DMPDPphys = allocpages(firstaddr, ndmpdpphys);
 	ndm1g = 0;
 	if ((amd_feature & AMDID_PAGE1GB) != 0)
 		ndm1g = ptoa(Maxmem) >> PDPSHIFT;
@@ -626,7 +638,7 @@ create_pagetables(vm_paddr_t *firstaddr)
 	p4_p[PML4PML4I] |= PG_RW | PG_V | PG_U;
 
 	/* Connect the Direct Map slot(s) up to the PML4. */
-	for (i = 0; i < NDMPML4E; i++) {
+	for (i = 0; i < ndmpdpphys; i++) {
 		p4_p[DMPML4I + i] = DMPDPphys + ptoa(i);
 		p4_p[DMPML4I + i] |= PG_RW | PG_V | PG_U;
 	}
@@ -1698,7 +1710,7 @@ pmap_pinit(pmap_t pmap)
 		pmap->pm_pml4[KPML4BASE + i] = (KPDPphys + (i << PAGE_SHIFT)) |
 		    PG_RW | PG_V | PG_U;
 	}
-	for (i = 0; i < NDMPML4E; i++) {
+	for (i = 0; i < ndmpdpphys; i++) {
 		pmap->pm_pml4[DMPML4I + i] = (DMPDPphys + (i << PAGE_SHIFT)) |
 		    PG_RW | PG_V | PG_U;
 	}
@@ -1955,7 +1967,7 @@ pmap_release(pmap_t pmap)
 
 	for (i = 0; i < NKPML4E; i++)	/* KVA */
 		pmap->pm_pml4[KPML4BASE + i] = 0;
-	for (i = 0; i < NDMPML4E; i++)	/* Direct Map */
+	for (i = 0; i < ndmpdpphys; i++)/* Direct Map */
 		pmap->pm_pml4[DMPML4I + i] = 0;
 	pmap->pm_pml4[PML4PML4I] = 0;	/* Recursive Mapping */