diff --git a/sys/dev/xen/debug/debug.c b/sys/dev/xen/debug/debug.c
index ec4585e64c62..c4562c02ed03 100644
--- a/sys/dev/xen/debug/debug.c
+++ b/sys/dev/xen/debug/debug.c
@@ -1,159 +1,157 @@
 /*
  * Copyright (c) 2015 Roger Pau Monné <roger.pau@citrix.com>
  * 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.
  *
  * 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>
 __FBSDID("$FreeBSD$");
 
 #include "opt_stack.h"
 #include "opt_ddb.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/bus.h>
 #include <sys/kernel.h>
 #include <sys/lock.h>
 #include <sys/module.h>
 #include <sys/mutex.h>
 #include <sys/pcpu.h>
 #include <sys/smp.h>
 #include <sys/stack.h>
 #include <sys/sbuf.h>
 
 #include <xen/xen-os.h>
 #include <xen/xen_intr.h>
 #include <xen/hypervisor.h>
 
 /*
  * Xen debug device
  *
  * Handles the VIRQ_DEBUG interrupt and prints the backtrace of each
  * vCPU on the Xen console.
  */
 
 DPCPU_DEFINE(xen_intr_handle_t, xendebug_handler);
 static struct mtx lock;
 static struct sbuf *buf;
 
 static int
 xendebug_drain(void *arg, const char *str, int len)
 {
 
 	HYPERVISOR_console_write(__DECONST(char *, str), len);
 	return (len);
 }
 
 extern void
 stack_capture(struct stack *st, register_t rbp);
 
 static int
-xendebug_filter(void *arg)
+xendebug_filter(void *arg __unused)
 {
 #if defined(STACK) && defined(DDB)
 	struct stack st;
-	struct trapframe *frame;
 
-	frame = arg;
 	stack_zero(&st);
 	stack_save(&st);
 
 	mtx_lock_spin(&lock);
 	sbuf_clear(buf);
 	xc_printf("Printing stack trace vCPU%d\n", PCPU_GET(vcpu_id));
 	stack_sbuf_print_ddb(buf, &st);
 	sbuf_finish(buf);
 	mtx_unlock_spin(&lock);
 #endif
 
 	return (FILTER_HANDLED);
 }
 
 static void
 xendebug_identify(driver_t *driver, device_t parent)
 {
 
 	KASSERT(xen_domain(),
 	    ("Trying to add Xen debug device to non-xen guest"));
 
 	if (!xen_has_percpu_evtchn())
 		return;
 
 	if (BUS_ADD_CHILD(parent, 0, "debug", 0) == NULL)
 		panic("Unable to add Xen debug device.");
 }
 
 static int
 xendebug_probe(device_t dev)
 {
 
 	device_set_desc(dev, "Xen debug handler");
 	return (BUS_PROBE_NOWILDCARD);
 }
 
 static int
 xendebug_attach(device_t dev)
 {
 	int i, error;
 
 	mtx_init(&lock, "xen-dbg", NULL, MTX_SPIN);
 	buf = sbuf_new(NULL, NULL, 1024, SBUF_FIXEDLEN);
 	if (buf == NULL)
 		panic("Unable to create sbuf for stack dump");
 	sbuf_set_drain(buf, xendebug_drain, NULL);
 
 	/* Bind an event channel to a VIRQ on each VCPU. */
 	CPU_FOREACH(i) {
 		error = xen_intr_bind_virq(dev, VIRQ_DEBUG, i, xendebug_filter,
 		    NULL, NULL, INTR_TYPE_TTY,
 		    DPCPU_ID_PTR(i, xendebug_handler));
 		if (error != 0) {
 			printf("Failed to bind VIRQ_DEBUG to vCPU %d: %d",
 			    i, error);
 			continue;
 		}
 		xen_intr_describe(DPCPU_ID_GET(i, xendebug_handler), "d%d", i);
 	}
 
 	return (0);
 }
 
 static device_method_t xendebug_methods[] = {
 	DEVMETHOD(device_identify, xendebug_identify),
 	DEVMETHOD(device_probe, xendebug_probe),
 	DEVMETHOD(device_attach, xendebug_attach),
 
 	DEVMETHOD_END
 };
 
 static driver_t xendebug_driver = {
 	"debug",
 	xendebug_methods,
 	0,
 };
 
 devclass_t xendebug_devclass;
 
 DRIVER_MODULE(xendebug, xenpv, xendebug_driver, xendebug_devclass, 0, 0);
 MODULE_DEPEND(xendebug, xenpv, 1, 1, 1);