[PATCH v6 03/12] vhost: Delete useless read memory barrier

From: "Eugenio Pérez" <eperezma@redhat.com>
To: qemu-devel@nongnu.org
Cc: Stefano Garzarella <sgarzare@redhat.com>,
	"Gonglei (Arei)" <arei.gonglei@huawei.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Liuxiangdong <liuxiangdong5@huawei.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	Gautam Dawar <gdawar@xilinx.com>,
	Laurent Vivier <lvivier@redhat.com>, Eli Cohen <eli@mellanox.com>,
	Zhu Lingshan <lingshan.zhu@intel.com>, Cindy Lu <lulu@redhat.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Parav Pandit <parav@mellanox.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Harpreet Singh Anand <hanand@xilinx.com>,
	Eric Blake <eblake@redhat.com>,
	Markus Armbruster <armbru@redhat.com>
Subject: [PATCH v6 03/12] vhost: Delete useless read memory barrier
Date: Thu,  4 Aug 2022 20:17:13 +0200	[thread overview]
Message-ID: <20220804181722.701067-4-eperezma@redhat.com> (raw)
In-Reply-To: <20220804181722.701067-1-eperezma@redhat.com>

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>
---
 hw/virtio/vhost-shadow-virtqueue.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
index e6eebd0e8d..1b49bf54f2 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);
 }
 
-- 
2.31.1


