diff --git a/sys/amd64/include/vmm.h b/sys/amd64/include/vmm.h
--- a/sys/amd64/include/vmm.h
+++ b/sys/amd64/include/vmm.h
@@ -686,6 +686,11 @@
 	struct vm_guest_paging paging;
 };
 
+#define IPI_CPUSETSIZE 256
+
+__BITSET_DEFINE(_ipi_cpuset, IPI_CPUSETSIZE);
+typedef struct _ipi_cpuset ipi_cpuset_t;
+
 struct vm_exit {
 	enum vm_exitcode	exitcode;
 	int			inst_length;	/* 0 means unknown */
@@ -756,7 +761,7 @@
 		struct {
 			uint32_t mode;
 			uint8_t vector;
-			cpuset_t dmask;
+			ipi_cpuset_t dmask;
 		} ipi;
 		struct vm_task_switch task_switch;
 	} u;
diff --git a/sys/amd64/vmm/io/vlapic.c b/sys/amd64/vmm/io/vlapic.c
--- a/sys/amd64/vmm/io/vlapic.c
+++ b/sys/amd64/vmm/io/vlapic.c
@@ -1146,7 +1146,10 @@
 		vmexit->exitcode = VM_EXITCODE_IPI;
 		vmexit->u.ipi.mode = mode;
 		vmexit->u.ipi.vector = vec;
-		vmexit->u.ipi.dmask = ipimask;
+		__BIT_ZERO(IPI_CPUSETSIZE, &vmexit->u.ipi.dmask);
+		memcpy(&vmexit->u.ipi.dmask, &ipimask,
+		    __bitset_words(min(CPU_SETSIZE, IPI_CPUSETSIZE)) *
+			(_BITSET_BITS / 8));
 
 		*retu = true;
 	}
@@ -1166,21 +1169,26 @@
 vm_handle_ipi(struct vcpu *vcpu, struct vm_exit *vme, bool *retu)
 {
 	struct vlapic *vlapic = vm_lapic(vcpu);
-	cpuset_t *dmask = &vme->u.ipi.dmask;
+	cpuset_t dmask;
 	uint8_t vec = vme->u.ipi.vector;
 
+	CPU_ZERO(&dmask);
+	memcpy(&dmask, &vme->u.ipi.dmask,
+	    __bitset_words(min(CPU_SETSIZE, IPI_CPUSETSIZE)) *
+		(_BITSET_BITS / 8));
+
 	*retu = true;
 	switch (vme->u.ipi.mode) {
 	case APIC_DELMODE_INIT: {
 		cpuset_t active, reinit;
 
 		active = vm_active_cpus(vcpu_vm(vcpu));
-		CPU_AND(&reinit, &active, dmask);
+		CPU_AND(&reinit, &active, &dmask);
 		if (!CPU_EMPTY(&reinit)) {
 			vm_smp_rendezvous(vcpu, reinit, vlapic_handle_init,
 			    NULL);
 		}
-		vm_await_start(vcpu_vm(vcpu), dmask);
+		vm_await_start(vcpu_vm(vcpu), &dmask);
 
 		if (!vlapic->ipi_exit)
 			*retu = false;
@@ -1191,9 +1199,9 @@
 		/*
 		 * Ignore SIPIs in any state other than wait-for-SIPI
 		 */
-		*dmask = vm_start_cpus(vcpu_vm(vcpu), dmask);
+		dmask = vm_start_cpus(vcpu_vm(vcpu), &dmask);
 
-		if (CPU_EMPTY(dmask)) {
+		if (CPU_EMPTY(&dmask)) {
 			*retu = false;
 			break;
 		}
@@ -1204,7 +1212,7 @@
 		 */
 		if (!vlapic->ipi_exit) {
 			vme->exitcode = VM_EXITCODE_SPINUP_AP;
-			vme->u.spinup_ap.vcpu = CPU_FFS(dmask) - 1;
+			vme->u.spinup_ap.vcpu = CPU_FFS(&dmask) - 1;
 			vme->u.spinup_ap.rip = vec << PAGE_SHIFT;
 		}
 
diff --git a/usr.sbin/bhyve/bhyverun.c b/usr.sbin/bhyve/bhyverun.c
--- a/usr.sbin/bhyve/bhyverun.c
+++ b/usr.sbin/bhyve/bhyverun.c
@@ -929,7 +929,7 @@
 	int i;
 	switch (vme->u.ipi.mode) {
 	case APIC_DELMODE_INIT:
-		CPU_FOREACH_ISSET(i, &vme->u.ipi.dmask) {
+		__BIT_FOREACH_ISSET(IPI_CPUSETSIZE, i, &vme->u.ipi.dmask) {
 			error = vm_suspend_cpu(vcpu_info[i].vcpu);
 			if (error) {
 				warnx("%s: failed to suspend cpu %d\n",
@@ -939,7 +939,7 @@
 		}
 		break;
 	case APIC_DELMODE_STARTUP:
-		CPU_FOREACH_ISSET(i, &vme->u.ipi.dmask) {
+		__BIT_FOREACH_ISSET(IPI_CPUSETSIZE, i, &vme->u.ipi.dmask) {
 			spinup_ap(vcpu_info[i].vcpu,
 			    vme->u.ipi.vector << PAGE_SHIFT);
 		}