From: Eugenio Pérez <eperezma@redhat.com>
Date: Tue, 23 Aug 2022 18:30:28 +0000 (+0200)
Subject: vhost: Delete useless read memory barrier
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=9e193cec5db949e4001070442a2f7de7042ef09b;p=qemu.git

vhost: Delete useless read memory barrier

As discussed in previous series [1], this memory barrier is useless with
the atomic read of used idx at vhost_svq_more_used. Deleting it.

[1] https://lists.nongnu.org/archive/html/qemu-devel/2022-07/msg02616.html

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---

diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
index b35aeef4bd..8df5296f24 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -509,9 +509,6 @@ size_t vhost_svq_poll(VhostShadowVirtqueue *svq)
         if (unlikely(g_get_monotonic_time() - start_us > 10e6)) {
             return 0;
         }
-
-        /* Make sure we read new used_idx */
-        smp_rmb();
     } while (true);
 }