From a311650ae6ad0c169ade2583f78aa519878ea13f Mon Sep 17 00:00:00 2001
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: Fri, 27 Oct 2017 16:11:13 +0300
Subject: [PATCH] virtio/ringtest: virtio_ring: fix up need_event math
last kicked event index must be updated unconditionally:
even if we don't need to kick, we do not want to re-check
the same entry for events.
Reported-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Jens Freimann <jfreimann@redhat.com>
---
tools/virtio/ringtest/virtio_ring_0_9.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/tools/virtio/ringtest/virtio_ring_0_9.c b/tools/virtio/ringtest/virtio_ring_0_9.c
index bbc3043b2fb1..5fd3fbcb9e57 100644
--- a/tools/virtio/ringtest/virtio_ring_0_9.c
+++ b/tools/virtio/ringtest/virtio_ring_0_9.c
@@ -225,16 +225,18 @@ bool enable_call()
void kick_available(void)
{
+ bool need;
+
/* Flush in previous flags write */
/* Barrier C (for pairing) */
smp_mb();
- if (!vring_need_event(vring_avail_event(&ring),
- guest.avail_idx,
- guest.kicked_avail_idx))
- return;
+ need = vring_need_event(vring_avail_event(&ring),
+ guest.avail_idx,
+ guest.kicked_avail_idx);
guest.kicked_avail_idx = guest.avail_idx;
- kick();
+ if (need)
+ kick();
}
/* host side */
@@ -316,14 +318,16 @@ bool use_buf(unsigned *lenp, void **bufp)
void call_used(void)
{
+ bool need;
+
/* Flush in previous flags write */
/* Barrier D (for pairing) */
smp_mb();
- if (!vring_need_event(vring_used_event(&ring),
- host.used_idx,
- host.called_used_idx))
- return;
+ need = vring_need_event(vring_used_event(&ring),
+ host.used_idx,
+ host.called_used_idx);
host.called_used_idx = host.used_idx;
- call();
+ if (need)
+ call();
}