diff --git a/sys/kern/kern_cpuset.c b/sys/kern/kern_cpuset.c
index 3bdb45e..7b15c8d 100644
--- a/sys/kern/kern_cpuset.c
+++ b/sys/kern/kern_cpuset.c
@@ -769,7 +769,20 @@ cpuset_init(void *arg)
 		panic("Can't set initial cpuset mask.\n");
 	cpuset_zero->cs_flags |= CPU_SET_RDONLY;
 }
-SYSINIT(cpuset, SI_SUB_SMP, SI_ORDER_ANY, cpuset_init, NULL);
+SYSINIT(cpuset, SI_SUB_SMP, SI_ORDER_MIDDLE, cpuset_init, NULL);
+
+int
+cpuset_zero_modify(cpuset_t *mask)
+{
+	int err;
+
+	mtx_lock_spin(&cpuset_lock);
+	cpuset_zero->cs_flags &= ~CPU_SET_RDONLY;
+	err = cpuset_modify(cpuset_zero, mask);
+	cpuset_zero->cs_flags |= CPU_SET_RDONLY;
+	mtx_unlock_spin(&cpuset_lock);
+	return (err);
+}
 
 #ifndef _SYS_SYSPROTO_H_
 struct cpuset_args {
diff --git a/sys/sys/cpuset.h b/sys/sys/cpuset.h
index 854fa29..de1a7dd 100644
--- a/sys/sys/cpuset.h
+++ b/sys/sys/cpuset.h
@@ -54,6 +54,7 @@ typedef	struct _cpuset {
 #define	CPU_COPY(f, t)	(void)(*(t) = *(f))
 #define	CPU_ISSET(n, p)	(((p)->__bits[(n)/_NCPUBITS] & __cpuset_mask(n)) != 0)
 #define	CPU_SET(n, p)	((p)->__bits[(n)/_NCPUBITS] |= __cpuset_mask(n))
+#define	CPU_SETMASK(mask, p)	((p)->__bits[0] = (mask))
 #define	CPU_ZERO(p) do {				\
 	__size_t __i;					\
 	for (__i = 0; __i < _NCPUWORDS; __i++)		\
@@ -178,6 +179,7 @@ extern cpuset_t *cpuset_root;
 struct prison;
 struct proc;
 
+int	cpuset_zero_modify(cpuset_t *mask);
 struct cpuset *cpuset_thread0(void);
 struct cpuset *cpuset_ref(struct cpuset *);
 void	cpuset_rel(struct cpuset *);
diff --git a/sys/amd64/amd64/mp_machdep.c b/sys/amd64/amd64/mp_machdep.c
index d0b0abf..35d2051 100644
--- a/sys/amd64/amd64/mp_machdep.c
+++ b/sys/amd64/amd64/mp_machdep.c
@@ -39,6 +39,7 @@ __FBSDID("$FreeBSD$");
 #ifdef GPROF 
 #include <sys/gmon.h>
 #endif
+#include <sys/cpuset.h>
 #include <sys/kernel.h>
 #include <sys/ktr.h>
 #include <sys/lock.h>
@@ -1442,6 +1443,7 @@ SYSINIT(start_aps, SI_SUB_SMP, SI_ORDER_FIRST, release_aps, NULL);
 static int
 sysctl_hlt_cpus(SYSCTL_HANDLER_ARGS)
 {
+	cpuset_t mask_set;
 	cpumask_t mask;
 	int error;
 
@@ -1450,18 +1452,25 @@ sysctl_hlt_cpus(SYSCTL_HANDLER_ARGS)
 	if (error || !req->newptr)
 		return (error);
 
+	if (!hyperthreading_allowed)
+		mask |= hyperthreading_cpus_mask;
+	if ((mask & all_cpus) == all_cpus)
+		mask &= ~(1<<0);
+
+	CPU_ZERO(&mask_set);
+	CPU_SETMASK(~mask & all_cpus, &mask_set);
+	error = cpuset_zero_modify(&mask_set);
+	if (error)
+		return (error);
+
 	if (logical_cpus_mask != 0 &&
 	    (mask & logical_cpus_mask) == logical_cpus_mask)
 		hlt_logical_cpus = 1;
 	else
 		hlt_logical_cpus = 0;
 
-	if (! hyperthreading_allowed)
-		mask |= hyperthreading_cpus_mask;
-
-	if ((mask & all_cpus) == all_cpus)
-		mask &= ~(1<<0);
 	hlt_cpus_mask = mask;
+
 	return (error);
 }
 SYSCTL_PROC(_machdep, OID_AUTO, hlt_cpus, CTLTYPE_INT|CTLFLAG_RW,
@@ -1471,6 +1480,8 @@ SYSCTL_PROC(_machdep, OID_AUTO, hlt_cpus, CTLTYPE_INT|CTLFLAG_RW,
 static int
 sysctl_hlt_logical_cpus(SYSCTL_HANDLER_ARGS)
 {
+	cpuset_t mask_set;
+	cpumask_t mask;
 	int disable, error;
 
 	disable = hlt_logical_cpus;
@@ -1478,17 +1489,24 @@ sysctl_hlt_logical_cpus(SYSCTL_HANDLER_ARGS)
 	if (error || !req->newptr)
 		return (error);
 
+	mask = hlt_cpus_mask;
 	if (disable)
-		hlt_cpus_mask |= logical_cpus_mask;
+		mask |= logical_cpus_mask;
 	else
-		hlt_cpus_mask &= ~logical_cpus_mask;
+		mask &= ~logical_cpus_mask;
 
-	if (! hyperthreading_allowed)
-		hlt_cpus_mask |= hyperthreading_cpus_mask;
+	if (!hyperthreading_allowed)
+		mask |= hyperthreading_cpus_mask;
 
-	if ((hlt_cpus_mask & all_cpus) == all_cpus)
-		hlt_cpus_mask &= ~(1<<0);
+	if ((mask & all_cpus) == all_cpus)
+		mask &= ~(1<<0);
 
+	CPU_ZERO(&mask_set);
+	CPU_SETMASK(~mask & all_cpus, &mask_set);
+	error = cpuset_zero_modify(&mask_set);
+	if (error != 0) 
+		return (error);
+	hlt_cpus_mask = mask;
 	hlt_logical_cpus = disable;
 	return (error);
 }
@@ -1496,6 +1514,8 @@ sysctl_hlt_logical_cpus(SYSCTL_HANDLER_ARGS)
 static int
 sysctl_hyperthreading_allowed(SYSCTL_HANDLER_ARGS)
 {
+	cpuset_t mask_set;
+	cpumask_t mask;
 	int allowed, error;
 
 	allowed = hyperthreading_allowed;
@@ -1503,30 +1523,27 @@ sysctl_hyperthreading_allowed(SYSCTL_HANDLER_ARGS)
 	if (error || !req->newptr)
 		return (error);
 
-#ifdef SCHED_ULE
-	/*
-	 * SCHED_ULE doesn't allow enabling/disabling HT cores at
-	 * run-time.
-	 */
-	if (allowed != hyperthreading_allowed)
-		return (ENOTSUP);
-	return (error);
-#endif
-
+	mask = hlt_cpus_mask;
 	if (allowed)
-		hlt_cpus_mask &= ~hyperthreading_cpus_mask;
+		mask &= ~hyperthreading_cpus_mask;
 	else
-		hlt_cpus_mask |= hyperthreading_cpus_mask;
+		mask |= hyperthreading_cpus_mask;
 
 	if (logical_cpus_mask != 0 &&
-	    (hlt_cpus_mask & logical_cpus_mask) == logical_cpus_mask)
+	    (mask & logical_cpus_mask) == logical_cpus_mask)
 		hlt_logical_cpus = 1;
 	else
 		hlt_logical_cpus = 0;
 
-	if ((hlt_cpus_mask & all_cpus) == all_cpus)
-		hlt_cpus_mask &= ~(1<<0);
+	if ((mask & all_cpus) == all_cpus)
+		mask &= ~(1<<0);
 
+	CPU_ZERO(&mask_set);
+	CPU_SETMASK(~mask & all_cpus, &mask_set);
+	error = cpuset_zero_modify(&mask_set);
+	if (error != 0) 
+		return (error);
+	hlt_cpus_mask = mask;
 	hyperthreading_allowed = allowed;
 	return (error);
 }
@@ -1534,6 +1551,7 @@ sysctl_hyperthreading_allowed(SYSCTL_HANDLER_ARGS)
 static void
 cpu_hlt_setup(void *dummy __unused)
 {
+	cpuset_t mask_set;
 
 	if (logical_cpus_mask != 0) {
 		TUNABLE_INT_FETCH("machdep.hlt_logical_cpus",
@@ -1564,6 +1582,9 @@ cpu_hlt_setup(void *dummy __unused)
 			if (! hyperthreading_allowed)
 				hlt_cpus_mask |= hyperthreading_cpus_mask;
 		}
+		CPU_ZERO(&mask_set);
+		CPU_SETMASK(~hlt_cpus_mask & all_cpus, &mask_set);
+		cpuset_zero_modify(&mask_set);
 	}
 }
 SYSINIT(cpu_hlt, SI_SUB_SMP, SI_ORDER_ANY, cpu_hlt_setup, NULL);