xen/evtchn: use smp barriers for user event ring
The ring buffer for user events is local to the given kernel instance,
so smp barriers are fine for ensuring consistency.
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Link: https://lore.kernel.org/r/20210219154030.10892-8-jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c
index a7a8571..421382c 100644
--- a/drivers/xen/evtchn.c
+++ b/drivers/xen/evtchn.c
@@ -173,7 +173,7 @@ static irqreturn_t evtchn_interrupt(int irq, void *data)
if ((u->ring_prod - u->ring_cons) < u->ring_size) {
*evtchn_ring_entry(u, u->ring_prod) = evtchn->port;
- wmb(); /* Ensure ring contents visible */
+ smp_wmb(); /* Ensure ring contents visible */
if (u->ring_cons == u->ring_prod++) {
wake_up_interruptible(&u->evtchn_wait);
kill_fasync(&u->evtchn_async_queue,
@@ -245,7 +245,7 @@ static ssize_t evtchn_read(struct file *file, char __user *buf,
}
rc = -EFAULT;
- rmb(); /* Ensure that we see the port before we copy it. */
+ smp_rmb(); /* Ensure that we see the port before we copy it. */
if (copy_to_user(buf, evtchn_ring_entry(u, c), bytes1) ||
((bytes2 != 0) &&
copy_to_user(&buf[bytes1], &u->ring[0], bytes2)))
