Commit d5669959 authored by Juergen Gross's avatar Juergen Gross Committed by Boris Ostrovsky
Browse files

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: default avatarAndrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Reviewed-by: default avatarJan Beulich <jbeulich@suse.com>
Link: https://lore.kernel.org/r/20210219154030.10892-8-jgross@suse.com


Signed-off-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
parent 06f45fe9

drivers/xen/evtchn.c

+2 −2
Original line number Diff line number Diff line
@@ -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)))