xen/netback: use lateeoi irq binding

commit 23025393dbeb3b8b3b60ebfa724cdae384992e27 upstream.

In order to reduce the chance for the system becoming unresponsive due
to event storms triggered by a misbehaving netfront use the lateeoi
irq binding for netback and unmask the event channel only just before
going to sleep waiting for new events.

Make sure not to issue an EOI when none is pending by introducing an
eoi_pending element to struct xenvif_queue.

When no request has been consumed set the spurious flag when sending
the EOI for an interrupt.

This is part of XSA-332.

Cc: stable@vger.kernel.org
Reported-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Wei Liu <wl@xen.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 13 insertions, 4 deletions

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 65d37257e033..ee7a800c16d5 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -670,6 +670,10 @@ void xenvif_napi_schedule_or_enable_events(struct xenvif_queue *queue)
 
 	if (more_to_do)
 		napi_schedule(&queue->napi);
+	else if (xenvif_atomic_fetch_andnot(NETBK_TX_EOI | NETBK_COMMON_EOI,
+				     &queue->eoi_pending) &
+		 (NETBK_TX_EOI | NETBK_COMMON_EOI))
+		xen_irq_lateeoi(queue->tx_irq, 0);
 }
 
 static void tx_add_credit(struct xenvif_queue *queue)
@@ -2010,14 +2014,14 @@ static bool xenvif_rx_queue_ready(struct xenvif_queue *queue)
 	return queue->stalled && prod - cons >= 1;
 }
 
-static bool xenvif_have_rx_work(struct xenvif_queue *queue)
+bool xenvif_have_rx_work(struct xenvif_queue *queue, bool test_kthread)
 {
 	return (!skb_queue_empty(&queue->rx_queue)
 		&& xenvif_rx_ring_slots_available(queue))
 		|| (queue->vif->stall_timeout &&
 		    (xenvif_rx_queue_stalled(queue)
 		     || xenvif_rx_queue_ready(queue)))
-		|| kthread_should_stop()
+		|| (test_kthread && kthread_should_stop())
 		|| queue->vif->disabled;
 }
 
@@ -2048,15 +2052,20 @@ static void xenvif_wait_for_rx_work(struct xenvif_queue *queue)
 {
 	DEFINE_WAIT(wait);
 
-	if (xenvif_have_rx_work(queue))
+	if (xenvif_have_rx_work(queue, true))
 		return;
 
 	for (;;) {
 		long ret;
 
 		prepare_to_wait(&queue->wq, &wait, TASK_INTERRUPTIBLE);
-		if (xenvif_have_rx_work(queue))
+		if (xenvif_have_rx_work(queue, true))
 			break;
+		if (xenvif_atomic_fetch_andnot(NETBK_RX_EOI | NETBK_COMMON_EOI,
+					&queue->eoi_pending) &
+		    (NETBK_RX_EOI | NETBK_COMMON_EOI))
+			xen_irq_lateeoi(queue->rx_irq, 0);
+
 		ret = schedule_timeout(xenvif_rx_queue_timeout(queue));
 		if (!ret)
 			break;