diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -497,8 +497,8 @@
 	.kva_min =	KV5ADDR(NPML5EPG / 2, 0, 0, 0, 0),	/* == rec_pt */
 	.dmap_low =	KV5ADDR(DMPML5I, 0, 0, 0, 0),
 	.dmap_high =	KV5ADDR(DMPML5I + NDMPML5E, 0, 0, 0, 0),
-	.lm_low =	KV4ADDR(LMSPML4I, 0, 0, 0),
-	.lm_high =	KV4ADDR(LMEPML4I + 1, 0, 0, 0),
+	.lm_low =	KV5ADDR(LMSPML5I, 0, 0, 0, 0),
+	.lm_high =	KV5ADDR(LMEPML5I + 1, 0, 0, 0, 0),
 	.km_low =	KV4ADDR(KPML4BASE, 0, 0, 0),
 	.km_high =	KV4ADDR(KPML4BASE + NKPML4E - 1, NPDPEPG - 1,
 			    NPDEPG - 1, NPTEPG - 1),
@@ -2475,6 +2475,7 @@
 	struct pmap_preinit_mapping *ppim;
 	vm_page_t m, mpte;
 	pml4_entry_t *pml4e;
+	unsigned long lm_max;
 	int error, i, ret, skz63;
 
 	/* L1TF, reserve page @0 unconditionally */
@@ -2600,10 +2601,15 @@
 
 	lm_ents = 8;
 	TUNABLE_INT_FETCH("vm.pmap.large_map_pml4_entries", &lm_ents);
-	if (lm_ents > LMEPML4I - LMSPML4I + 1)
-		lm_ents = LMEPML4I - LMSPML4I + 1;
+	lm_max = (kva_layout.lm_high - kva_layout.lm_low) / NBPML4;
+	if (lm_ents > lm_max) {
+		printf(
+	    "pmap: shrinking large map from requested %d slots to %ld slots\n",
+		    lm_ents, lm_max);
+		lm_ents = lm_max;
+	}
 #ifdef KMSAN
-	if (lm_ents > KMSANORIGPML4I - LMSPML4I) {
+	if (!la57 && lm_ents > KMSANORIGPML4I - LMSPML4I) {
 		printf(
 	    "pmap: shrinking large map for KMSAN (%d slots to %ld slots)\n",
 		    lm_ents, KMSANORIGPML4I - LMSPML4I);
@@ -2615,12 +2621,20 @@
 		    lm_ents, (u_long)lm_ents * (NBPML4 / 1024 / 1024 / 1024));
 	if (lm_ents != 0) {
 		large_vmem = vmem_create("large", kva_layout.lm_low,
-		    (vmem_size_t)kva_layout.lm_high - kva_layout.lm_low,
-		    PAGE_SIZE, 0, M_WAITOK);
+		    (vmem_size_t)lm_ents * NBPML4, PAGE_SIZE, 0, M_WAITOK);
 		if (large_vmem == NULL) {
 			printf("pmap: cannot create large map\n");
 			lm_ents = 0;
 		}
+		if (la57) {
+			for (i = LMSPML5I; i < howmany((vm_offset_t)NBPML4 *
+			    lm_ents, NBPML5); i++) {
+				m = pmap_large_map_getptp_unlocked();
+				kernel_pmap->pm_pmltop[i] = X86_PG_V |
+				    X86_PG_RW | X86_PG_A | X86_PG_M |
+				    pg_nx | VM_PAGE_TO_PHYS(m);
+			}
+		}
 		for (i = 0; i < lm_ents; i++) {
 			m = pmap_large_map_getptp_unlocked();
 			pml4e = pmap_pml4e(kernel_pmap, kva_layout.lm_low +
diff --git a/sys/amd64/include/pmap.h b/sys/amd64/include/pmap.h
--- a/sys/amd64/include/pmap.h
+++ b/sys/amd64/include/pmap.h
@@ -202,9 +202,14 @@
 #define	KMSANSHADPML4I	(KPML4BASE - NKMSANSHADPML4E)
 #define	KMSANORIGPML4I	(DMPML4I - NKMSANORIGPML4E)
 
-/* Large map: index of the first and max last pml4 entry */
+/*
+ * Large map: index of the first and max last pml4/la48 and pml5/la57
+ * entry.
+ */
 #define	LMSPML4I	(PML4PML4I + 1)
 #define	LMEPML4I	(KASANPML4I - 1)
+#define	LMSPML5I	(DMPML5I + NDMPML5E)
+#define	LMEPML5I	(LMSPML5I + 32 - 1)	/* 32 slots for large map */
 
 /*
  * XXX doesn't really belong here I guess...
diff --git a/sys/amd64/include/vmparam.h b/sys/amd64/include/vmparam.h
--- a/sys/amd64/include/vmparam.h
+++ b/sys/amd64/include/vmparam.h
@@ -181,9 +181,9 @@
  * 0x0100000000000000 - 0xf0ffffffffffffff   does not exist (hole)
  * 0xff00000000000000 - 0xff00ffffffffffff   recursive page table (2048TB slot)
  * 0xff01000000000000 - 0xff20ffffffffffff   direct map (32 x 2048TB slots)
- * 0xff21000000000000 - 0xffff807fffffffff   unused
- * 0xffff808000000000 - 0xffff847fffffffff   large map (can be tuned up)
- * 0xffff848000000000 - 0xfffff77fffffffff   unused (large map extends there)
+ * 0xff21000000000000 - 0xff40ffffffffffff   large map
+ * 0xff41000000000000 - 0xffff7fffffffffff   unused
+ * 0xffff800000000000 - 0xfffff5ffffffffff   unused (start of kernel pml4 entry)
  * 0xfffff60000000000 - 0xfffff7ffffffffff   2TB KMSAN origin map, optional
  * 0xfffff78000000000 - 0xfffff7bfffffffff   512GB KASAN shadow map, optional
  * 0xfffff80000000000 - 0xfffffbffffffffff   4TB unused