Index: head/sys/amd64/amd64/machdep.c
===================================================================
--- head/sys/amd64/amd64/machdep.c
+++ head/sys/amd64/amd64/machdep.c
@@ -670,10 +670,10 @@
 static struct gate_descriptor idt0[NIDT];
 struct gate_descriptor *idt = &idt0[0];	/* interrupt descriptor table */
 
-static char dblfault_stack[PAGE_SIZE] __aligned(16);
-static char mce0_stack[PAGE_SIZE] __aligned(16);
-static char nmi0_stack[PAGE_SIZE] __aligned(16);
-static char dbg0_stack[PAGE_SIZE] __aligned(16);
+static char dblfault_stack[DBLFAULT_STACK_SIZE] __aligned(16);
+static char mce0_stack[MCE_STACK_SIZE] __aligned(16);
+static char nmi0_stack[NMI_STACK_SIZE] __aligned(16);
+static char dbg0_stack[DBG_STACK_SIZE] __aligned(16);
 CTASSERT(sizeof(struct nmi_pcpu) == 16);
 
 /*
Index: head/sys/amd64/amd64/mp_machdep.c
===================================================================
--- head/sys/amd64/amd64/mp_machdep.c
+++ head/sys/amd64/amd64/mp_machdep.c
@@ -305,22 +305,22 @@
 	pc->pc_common_tss.tss_rsp0 = 0;
 
 	/* The doublefault stack runs on IST1. */
-	np = ((struct nmi_pcpu *)&doublefault_stack[PAGE_SIZE]) - 1;
+	np = ((struct nmi_pcpu *)&doublefault_stack[DBLFAULT_STACK_SIZE]) - 1;
 	np->np_pcpu = (register_t)pc;
 	pc->pc_common_tss.tss_ist1 = (long)np;
 
 	/* The NMI stack runs on IST2. */
-	np = ((struct nmi_pcpu *) &nmi_stack[PAGE_SIZE]) - 1;
+	np = ((struct nmi_pcpu *)&nmi_stack[NMI_STACK_SIZE]) - 1;
 	np->np_pcpu = (register_t)pc;
 	pc->pc_common_tss.tss_ist2 = (long)np;
 
 	/* The MC# stack runs on IST3. */
-	np = ((struct nmi_pcpu *) &mce_stack[PAGE_SIZE]) - 1;
+	np = ((struct nmi_pcpu *)&mce_stack[MCE_STACK_SIZE]) - 1;
 	np->np_pcpu = (register_t)pc;
 	pc->pc_common_tss.tss_ist3 = (long)np;
 
 	/* The DB# stack runs on IST4. */
-	np = ((struct nmi_pcpu *) &dbg_stack[PAGE_SIZE]) - 1;
+	np = ((struct nmi_pcpu *)&dbg_stack[DBG_STACK_SIZE]) - 1;
 	np->np_pcpu = (register_t)pc;
 	pc->pc_common_tss.tss_ist4 = (long)np;
 
@@ -481,13 +481,14 @@
 		/* allocate and set up an idle stack data page */
 		bootstacks[cpu] = (void *)kmem_malloc(kstack_pages * PAGE_SIZE,
 		    M_WAITOK | M_ZERO);
-		doublefault_stack = (char *)kmem_malloc(PAGE_SIZE, M_WAITOK |
-		    M_ZERO);
-		mce_stack = (char *)kmem_malloc(PAGE_SIZE, M_WAITOK | M_ZERO);
+		doublefault_stack = (char *)kmem_malloc(DBLFAULT_STACK_SIZE,
+		    M_WAITOK | M_ZERO);
+		mce_stack = (char *)kmem_malloc(MCE_STACK_SIZE,
+		    M_WAITOK | M_ZERO);
 		nmi_stack = (char *)kmem_malloc_domainset(
-		    DOMAINSET_PREF(domain), PAGE_SIZE, M_WAITOK | M_ZERO);
+		    DOMAINSET_PREF(domain), NMI_STACK_SIZE, M_WAITOK | M_ZERO);
 		dbg_stack = (char *)kmem_malloc_domainset(
-		    DOMAINSET_PREF(domain), PAGE_SIZE, M_WAITOK | M_ZERO);
+		    DOMAINSET_PREF(domain), DBG_STACK_SIZE, M_WAITOK | M_ZERO);
 		dpcpu = (void *)kmem_malloc_domainset(DOMAINSET_PREF(domain),
 		    DPCPU_SIZE, M_WAITOK | M_ZERO);
 
Index: head/sys/amd64/amd64/pmap.c
===================================================================
--- head/sys/amd64/amd64/pmap.c
+++ head/sys/amd64/amd64/pmap.c
@@ -157,6 +157,7 @@
 #include <x86/ifunc.h>
 #include <machine/cpu.h>
 #include <machine/cputypes.h>
+#include <machine/intr_machdep.h>
 #include <machine/md_var.h>
 #include <machine/pcb.h>
 #include <machine/specialreg.h>
@@ -10481,17 +10482,17 @@
 	CPU_FOREACH(i) {
 		/* Doublefault stack IST 1 */
 		va = __pcpu[i].pc_common_tss.tss_ist1 + sizeof(struct nmi_pcpu);
-		pmap_pti_add_kva_locked(va - PAGE_SIZE, va, false);
+		pmap_pti_add_kva_locked(va - DBLFAULT_STACK_SIZE, va, false);
 		/* NMI stack IST 2 */
 		va = __pcpu[i].pc_common_tss.tss_ist2 + sizeof(struct nmi_pcpu);
-		pmap_pti_add_kva_locked(va - PAGE_SIZE, va, false);
+		pmap_pti_add_kva_locked(va - NMI_STACK_SIZE, va, false);
 		/* MC# stack IST 3 */
 		va = __pcpu[i].pc_common_tss.tss_ist3 +
 		    sizeof(struct nmi_pcpu);
-		pmap_pti_add_kva_locked(va - PAGE_SIZE, va, false);
+		pmap_pti_add_kva_locked(va - MCE_STACK_SIZE, va, false);
 		/* DB# stack IST 4 */
 		va = __pcpu[i].pc_common_tss.tss_ist4 + sizeof(struct nmi_pcpu);
-		pmap_pti_add_kva_locked(va - PAGE_SIZE, va, false);
+		pmap_pti_add_kva_locked(va - DBG_STACK_SIZE, va, false);
 	}
 	pmap_pti_add_kva_locked((vm_offset_t)kernphys + KERNBASE,
 	    (vm_offset_t)etext, true);
Index: head/sys/amd64/include/intr_machdep.h
===================================================================
--- head/sys/amd64/include/intr_machdep.h
+++ head/sys/amd64/include/intr_machdep.h
@@ -41,4 +41,9 @@
 	register_t	__padding;	/* pad to 16 bytes */
 };
 
+#define	DBLFAULT_STACK_SIZE	PAGE_SIZE
+#define	NMI_STACK_SIZE		PAGE_SIZE
+#define	MCE_STACK_SIZE		PAGE_SIZE
+#define	DBG_STACK_SIZE		PAGE_SIZE
+
 #endif	/* !__MACHINE_INTR_MACHDEP_H__ */