diff --git a/usr.bin/rump_allserver/rump_allserver.1 b/usr.bin/rump_allserver/rump_allserver.1
index 0c1c8e04a762..02d595908dce 100644
--- a/usr.bin/rump_allserver/rump_allserver.1
+++ b/usr.bin/rump_allserver/rump_allserver.1
@@ -1,4 +1,4 @@
-.\"	$NetBSD: rump_allserver.1,v 1.6 2010/12/15 18:42:59 pooka Exp $
+.\"	$NetBSD: rump_allserver.1,v 1.7 2011/01/03 10:44:40 pooka Exp $
 .\"
 .\" Copyright (c) 2010 Antti Kantee.  All rights reserved.
 .\"
@@ -23,7 +23,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd December 14, 2010
+.Dd January 3, 2011
 .Dt RUMP_SERVER 1
 .Os
 .Sh NAME
@@ -33,6 +33,7 @@
 .Sh SYNOPSIS
 .Nm
 .Op Fl s
+.Op Fl c Ar ncpu
 .Op Fl d Ar drivespec
 .Op Fl l Ar library
 .Op Fl m Ar module
@@ -60,6 +61,12 @@ system was built.
 At execution time it is possible to load components from the command
 line as described in the options section.
 .Bl -tag -width indent
+.It Fl c Ar ncpu
+Configure
+.Ar ncpu
+virtual CPUs on SMP-capable archs.
+By default, the number of CPUs equals the number of CPUs on the
+host.
 .It Fl d Ar drivespec
 The argument
 .Ar drivespec
diff --git a/usr.bin/rump_allserver/rump_allserver.c b/usr.bin/rump_allserver/rump_allserver.c
index 9fd21da8f49b..e70f1630851c 100644
--- a/usr.bin/rump_allserver/rump_allserver.c
+++ b/usr.bin/rump_allserver/rump_allserver.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: rump_allserver.c,v 1.11 2010/12/15 19:07:43 pooka Exp $	*/
+/*	$NetBSD: rump_allserver.c,v 1.12 2011/01/03 10:44:40 pooka Exp $	*/
 
 /*-
  * Copyright (c) 2010 Antti Kantee.  All Rights Reserved.
@@ -27,7 +27,7 @@
 
 #include <sys/cdefs.h>
 #ifndef lint
-__RCSID("$NetBSD: rump_allserver.c,v 1.11 2010/12/15 19:07:43 pooka Exp $");
+__RCSID("$NetBSD: rump_allserver.c,v 1.12 2011/01/03 10:44:40 pooka Exp $");
 #endif /* !lint */
 
 #include <sys/types.h>
@@ -51,8 +51,8 @@ static void
 usage(void)
 {
 
-	fprintf(stderr, "usage: %s [-s] [-d drivespec] [-l libs] [-m modules] "
-	    "bindurl\n", getprogname());
+	fprintf(stderr, "usage: %s [-s] [-c ncpu] [-d drivespec] [-l libs] "
+	    "[-m modules] bindurl\n", getprogname());
 	exit(1);
 }
 
@@ -101,12 +101,21 @@ main(int argc, char *argv[])
 	unsigned netfs = 0, curetfs = 0;
 	int error;
 	int ch, sflag;
+	int ncpu;
 
 	setprogname(argv[0]);
 
 	sflag = 0;
-	while ((ch = getopt(argc, argv, "d:l:m:s")) != -1) {
+	while ((ch = getopt(argc, argv, "c:d:l:m:s")) != -1) {
 		switch (ch) {
+		case 'c':
+			ncpu = atoi(optarg);
+			/* XXX: MAXCPUS is from host, not from kernel */
+			if (ncpu < 1 || ncpu > MAXCPUS)
+				err(1, "CPU count needs to be between "
+				    "1 and %d\n", MAXCPUS);
+			setenv("RUMP_NCPU", optarg, 1);
+			break;
 		case 'd': {
 			char *options, *value;
 			char *key, *hostpath;