From e94160fef4c2058ef30703accafc2a42ebe21286 Mon Sep 17 00:00:00 2001
From: mikeb <mikeb@openbsd.org>
Date: Wed, 3 Aug 2016 17:14:41 +0000
Subject: [PATCH] Use atomic operations to manipulate event masking bits

---
 sys/dev/pv/xen.c    | 12 +++++-------
 sys/dev/pv/xenvar.h | 14 +++++++++++++-
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/sys/dev/pv/xen.c b/sys/dev/pv/xen.c
index 8f4be60e649..2ec7c4c7230 100644
--- a/sys/dev/pv/xen.c
+++ b/sys/dev/pv/xen.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: xen.c,v 1.59 2016/08/03 14:55:57 mikeb Exp $	*/
+/*	$OpenBSD: xen.c,v 1.60 2016/08/03 17:14:41 mikeb Exp $	*/
 
 /*
  * Copyright (c) 2015 Mike Belopuhov
@@ -743,7 +743,7 @@ xen_intr_establish(evtchn_port_t port, xen_intr_handle_t *xih, int domain,
 	SLIST_INSERT_HEAD(&sc->sc_intrs, xi, xi_entry);
 
 	/* Mask the event port */
-	setbit((char *)&sc->sc_ipg->evtchn_mask[0], xi->xi_port);
+	atomic_setbit_ptr(&sc->sc_ipg->evtchn_mask[0], xi->xi_port);
 
 #if defined(XEN_DEBUG) && disabled
 	memset(&es, 0, sizeof(es));
@@ -789,9 +789,8 @@ xen_intr_disestablish(xen_intr_handle_t xih)
 
 	taskq_destroy(xi->xi_taskq);
 
-	setbit((char *)&sc->sc_ipg->evtchn_mask[0], xi->xi_port);
-	clrbit((char *)&sc->sc_ipg->evtchn_pending[0], xi->xi_port);
-	virtio_membar_sync();
+	atomic_setbit_ptr(&sc->sc_ipg->evtchn_mask[0], xi->xi_port);
+	atomic_clearbit_ptr(&sc->sc_ipg->evtchn_pending[0], xi->xi_port);
 
 	if (!xi->xi_noclose) {
 		ec.port = xi->xi_port;
@@ -837,8 +836,7 @@ xen_intr_mask(xen_intr_handle_t xih)
 
 	if ((xi = xen_lookup_intsrc(sc, port)) != NULL) {
 		xi->xi_masked = 1;
-		setbit((char *)&sc->sc_ipg->evtchn_mask[0], xi->xi_port);
-		virtio_membar_sync();
+		atomic_setbit_ptr(&sc->sc_ipg->evtchn_mask[0], xi->xi_port);
 	}
 }
 
diff --git a/sys/dev/pv/xenvar.h b/sys/dev/pv/xenvar.h
index a3cb403499a..428002d6a72 100644
--- a/sys/dev/pv/xenvar.h
+++ b/sys/dev/pv/xenvar.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: xenvar.h,v 1.34 2016/08/03 14:55:58 mikeb Exp $	*/
+/*	$OpenBSD: xenvar.h,v 1.35 2016/08/03 17:14:41 mikeb Exp $	*/
 
 /*
  * Copyright (c) 2015 Mike Belopuhov
@@ -143,6 +143,18 @@ struct xs_transaction {
 	struct xs_softc		*xst_sc;
 };
 
+static inline int
+atomic_setbit_ptr(volatile void *ptr, int bit)
+{
+	int obit;
+
+	__asm__ __volatile__ ("lock btsl %2,%1; sbbl %0,%0" :
+	    "=r" (obit), "=m" (*(volatile long *)ptr) : "Ir" (bit) :
+	    "memory");
+
+	return (obit);
+}
+
 static inline int
 atomic_clearbit_ptr(volatile void *ptr, int bit)
 {
-- 
2.20.1