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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>
master
Juergen Gross 2021-02-19 16:40:29 +01:00 committed by Boris Ostrovsky
parent 06f45fe96f
commit d566995940
1 changed files with 2 additions and 2 deletions
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4
drivers/xen/evtchn.c
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@ -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)))