diff --git a/sys/arm64/arm64/sys_machdep.c b/sys/arm64/arm64/sys_machdep.c
index c50b745cfba0..aba864b9526e 100644
--- a/sys/arm64/arm64/sys_machdep.c
+++ b/sys/arm64/arm64/sys_machdep.c
@@ -1,42 +1,62 @@
 /*-
  * Copyright (c) 2015 The FreeBSD Foundation
  *
  * This software was developed by Andrew Turner under
  * sponsorship from the FreeBSD Foundation.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
  */
 
 #include <sys/cdefs.h>
 #include <sys/param.h>
+#include <sys/proc.h>
 #include <sys/systm.h>
 #include <sys/sysproto.h>
 
+#include <machine/pcb.h>
 #include <machine/sysarch.h>
 
+#include <security/audit/audit.h>
+
 int
 sysarch(struct thread *td, struct sysarch_args *uap)
 {
+	struct pcb *pcb;
+	unsigned long sve_len;
+	int error;
+
+	switch (uap->op) {
+	case ARM64_GET_SVE_VL:
+		pcb = td->td_pcb;
+		sve_len = pcb->pcb_sve_len;
+		error = EINVAL;
+		if (sve_len != 0)
+			error = copyout(&sve_len, uap->parms, sizeof(sve_len));
+		break;
+	default:
+		error = EINVAL;
+		break;
+	}
 
-	return (ENOTSUP);
+	return (error);
 }
diff --git a/sys/arm64/include/sysarch.h b/sys/arm64/include/sysarch.h
index 2bd45d384743..f72d3427602e 100644
--- a/sys/arm64/include/sysarch.h
+++ b/sys/arm64/include/sysarch.h
@@ -1,52 +1,55 @@
 /*-
  * Copyright (c) 1993 The Regents of the University of California.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
  *	from: FreeBSD: src/sys/i386/include/sysarch.h,v 1.14 2000/09/21
  */
 
 #ifdef __arm__
 #include <arm/sysarch.h>
 #else /* !__arm__ */
 
 /*
  * Architecture specific syscalls (arm64)
  */
 #ifndef _MACHINE_SYSARCH_H_
 #define	_MACHINE_SYSARCH_H_
 
+#define	ARM64_GET_SVE_VL	0x200
+/* Reserved ARM64_SET_SVE_VL	0x201 */
+
 #ifndef _KERNEL
 
 __BEGIN_DECLS
 int	sysarch(int _number, void *_args);
 __END_DECLS
 
 #endif
 
 #endif /* !_MACHINE_SYSARCH_H_ */
 
 #endif /* !__arm__ */