diff --git a/lib/libc/gen/sched_getaffinity.c b/lib/libc/gen/sched_getaffinity.c
--- a/lib/libc/gen/sched_getaffinity.c
+++ b/lib/libc/gen/sched_getaffinity.c
@@ -35,7 +35,7 @@
 {
 	int error;
 
-	error = cpuset_getaffinity(CPU_LEVEL_WHICH, CPU_WHICH_PID,
+	error = cpuset_getaffinity(CPU_LEVEL_WHICH, CPU_WHICH_TIDPID,
 	    pid == 0 ? -1 : pid, cpusetsz, cpuset);
 	if (error == -1 && errno == ERANGE)
 		errno = EINVAL;
diff --git a/lib/libc/gen/sched_setaffinity.c b/lib/libc/gen/sched_setaffinity.c
--- a/lib/libc/gen/sched_setaffinity.c
+++ b/lib/libc/gen/sched_setaffinity.c
@@ -58,7 +58,7 @@
 			if (cpu > mp_maxid)
 				CPU_CLR(cpu, &c);
 	}
-	error = cpuset_setaffinity(CPU_LEVEL_WHICH, CPU_WHICH_PID,
+	error = cpuset_setaffinity(CPU_LEVEL_WHICH, CPU_WHICH_TIDPID,
 	    pid == 0 ? -1 : pid, sizeof(cpuset_t), &c);
 	if (error == -1 && errno == EDEADLK)
 		errno = EINVAL;
diff --git a/lib/libc/sys/cpuset.2 b/lib/libc/sys/cpuset.2
--- a/lib/libc/sys/cpuset.2
+++ b/lib/libc/sys/cpuset.2
@@ -26,7 +26,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 3, 2017
+.Dd January 28, 2023
 .Dt CPUSET 2
 .Os
 .Sh NAME
@@ -100,6 +100,7 @@
 .Bl -column CPU_WHICH_INTRHANDLER -offset indent
 .It Dv CPU_WHICH_TID Ta "id is lwpid_t (thread id)"
 .It Dv CPU_WHICH_PID Ta "id is pid_t (process id)"
+.It Dv CPU_WHICH_TIDPID Ta "id is lwpid_t (thread id) or id is pid_t (process id)"
 .It Dv CPU_WHICH_JAIL Ta "id is jid (jail id)"
 .It Dv CPU_WHICH_CPUSET Ta "id is a cpusetid_t (cpuset id)"
 .It Dv CPU_WHICH_IRQ Ta "id is an irq number"
@@ -115,6 +116,7 @@
 of
 .Dv CPU_WHICH_TID ,
 .Dv CPU_WHICH_PID ,
+.Dv CPU_WHICH_TIDPID ,
 or
 .Dv CPU_WHICH_CPUSET
 to mean the current thread, process, or current thread's
diff --git a/sys/kern/kern_cpuset.c b/sys/kern/kern_cpuset.c
--- a/sys/kern/kern_cpuset.c
+++ b/sys/kern/kern_cpuset.c
@@ -150,6 +150,8 @@
 cpuset_t *cpuset_root;
 cpuset_t cpuset_domain[MAXMEMDOM];
 
+static int cpuset_which2(cpuwhich_t *, id_t, struct proc **, struct thread **,
+    struct cpuset **);
 static int domainset_valid(const struct domainset *, const struct domainset *);
 
 /*
@@ -972,6 +974,20 @@
 	return (0);
 }
 
+static int
+cpuset_which2(cpuwhich_t *which, id_t id, struct proc **pp, struct thread **tdp,
+    struct cpuset **setp)
+{
+
+	if (*which == CPU_WHICH_TIDPID) {
+		if (id == -1 || id > PID_MAX)
+			*which = CPU_WHICH_TID;
+		else
+			*which = CPU_WHICH_PID;
+	}
+	return (cpuset_which(*which, id, pp, tdp, setp));
+}
+
 static int
 cpuset_testshadow(struct cpuset *set, const cpuset_t *mask,
     const struct domainset *domain)
@@ -1739,7 +1755,11 @@
 	if (IN_CAPABILITY_MODE(td)) {
 		if (level != CPU_LEVEL_WHICH)
 			return (ECAPMODE);
-		if (which != CPU_WHICH_TID && which != CPU_WHICH_PID)
+		if (which != CPU_WHICH_TID && which != CPU_WHICH_PID &&
+		    which != CPU_WHICH_TIDPID)
+			return (ECAPMODE);
+		if (id != -1 && which == CPU_WHICH_TIDPID &&
+		    id != td->td_tid && id != td->td_proc->p_pid)
 			return (ECAPMODE);
 		if (id != -1 &&
 		    !(which == CPU_WHICH_TID && id == td->td_tid) &&
@@ -1876,7 +1896,7 @@
 
 	if (level == CPU_LEVEL_WHICH && which != CPU_WHICH_CPUSET)
 		return (EINVAL);
-	error = cpuset_which(which, id, &p, &ttd, &set);
+	error = cpuset_which2(&which, id, &p, &ttd, &set);
 	if (error)
 		return (error);
 	switch (which) {
@@ -1943,7 +1963,7 @@
 	error = cpuset_check_capabilities(td, level, which, id);
 	if (error != 0)
 		return (error);
-	error = cpuset_which(which, id, &p, &ttd, &set);
+	error = cpuset_which2(&which, id, &p, &ttd, &set);
 	if (error != 0)
 		return (error);
 	switch (level) {
@@ -2099,7 +2119,7 @@
 	switch (level) {
 	case CPU_LEVEL_ROOT:
 	case CPU_LEVEL_CPUSET:
-		error = cpuset_which(which, id, &p, &ttd, &set);
+		error = cpuset_which2(&which, id, &p, &ttd, &set);
 		if (error)
 			break;
 		switch (which) {
@@ -2135,6 +2155,13 @@
 		case CPU_WHICH_PID:
 			error = cpuset_setproc(id, NULL, mask, NULL, false);
 			break;
+		case CPU_WHICH_TIDPID:
+			if (id > PID_MAX || id == -1)
+				error = cpuset_setthread(id, mask);
+			else
+				error = cpuset_setproc(id, NULL, mask, NULL,
+				    false);
+			break;
 		case CPU_WHICH_CPUSET:
 		case CPU_WHICH_JAIL:
 			error = cpuset_which(which, id, &p, &ttd, &set);
@@ -2243,7 +2270,7 @@
 		return (error);
 	mask = malloc(domainsetsize, M_TEMP, M_WAITOK | M_ZERO);
 	bzero(&outset, sizeof(outset));
-	error = cpuset_which(which, id, &p, &ttd, &set);
+	error = cpuset_which2(&which, id, &p, &ttd, &set);
 	if (error)
 		goto out;
 	switch (level) {
@@ -2425,13 +2452,12 @@
 	 */
 	if (domainset_empty_vm(&domain))
 		domainset_copy(domainset2, &domain);
-
+	error = cpuset_which2(&which, id, &p, &ttd, &set);
+	if (error != 0)
+		goto out;
 	switch (level) {
 	case CPU_LEVEL_ROOT:
 	case CPU_LEVEL_CPUSET:
-		error = cpuset_which(which, id, &p, &ttd, &set);
-		if (error)
-			break;
 		switch (which) {
 		case CPU_WHICH_TID:
 		case CPU_WHICH_PID:
@@ -2468,11 +2494,8 @@
 			break;
 		case CPU_WHICH_CPUSET:
 		case CPU_WHICH_JAIL:
-			error = cpuset_which(which, id, &p, &ttd, &set);
-			if (error == 0) {
-				error = cpuset_modify_domain(set, &domain);
-				cpuset_rel(set);
-			}
+			error = cpuset_modify_domain(set, &domain);
+			cpuset_rel(set);
 			break;
 		case CPU_WHICH_IRQ:
 		case CPU_WHICH_INTRHANDLER:
diff --git a/sys/sys/cpuset.h b/sys/sys/cpuset.h
--- a/sys/sys/cpuset.h
+++ b/sys/sys/cpuset.h
@@ -109,6 +109,7 @@
 #define	CPU_WHICH_DOMAIN	6	/* Specifies a NUMA domain id. */
 #define	CPU_WHICH_INTRHANDLER	7	/* Specifies an irq # (not ithread). */
 #define	CPU_WHICH_ITHREAD	8	/* Specifies an irq's ithread. */
+#define	CPU_WHICH_TIDPID	9	/* Specifies a process or thread id. */
 
 /*
  * Reserved cpuset identifiers.