From 773d1bb4e9ea9ca704372e52569955937f91f15c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= <eperezma@redhat.com>
Date: Tue, 23 Aug 2022 20:30:28 +0200
Subject: [PATCH 13/23] vhost: Delete useless read memory barrier
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RH-Author: Eugenio Pérez <eperezma@redhat.com>
RH-MergeRequest: 116: vdpa: Restore device state on destination
RH-Bugzilla: 2114060
RH-Acked-by: Cindy Lu <lulu@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Commit: [12/21] 0e238fe934b1fc2c7e10b6f693468bc25ea3243f (eperezmartin/qemu-kvm)
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2114060
Upstream status: git@github.com:jasowang/qemu.git net-next
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>
(cherry picked from commit cdfb1612ba0f9b76367c96ce26ba94fedc7a0e61)
---
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 7792f3db1d..d36afbc547 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