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From 773d1bb4e9ea9ca704372e52569955937f91f15c Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= <eperezma@redhat.com>
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Date: Tue, 23 Aug 2022 20:30:28 +0200
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Subject: [PATCH 13/23] vhost: Delete useless read memory barrier
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Eugenio Pérez <eperezma@redhat.com>
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RH-MergeRequest: 116: vdpa: Restore device state on destination
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RH-Bugzilla: 2114060
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RH-Acked-by: Cindy Lu <lulu@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Commit: [12/21] 0e238fe934b1fc2c7e10b6f693468bc25ea3243f (eperezmartin/qemu-kvm)
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2114060
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Upstream status: git@github.com:jasowang/qemu.git net-next
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As discussed in previous series [1], this memory barrier is useless with
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the atomic read of used idx at vhost_svq_more_used. Deleting it.
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[1] https://lists.nongnu.org/archive/html/qemu-devel/2022-07/msg02616.html
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Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
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Acked-by: Jason Wang <jasowang@redhat.com>
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Signed-off-by: Jason Wang <jasowang@redhat.com>
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(cherry picked from commit cdfb1612ba0f9b76367c96ce26ba94fedc7a0e61)
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---
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hw/virtio/vhost-shadow-virtqueue.c | 3 ---
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1 file changed, 3 deletions(-)
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diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
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index 7792f3db1d..d36afbc547 100644
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--- a/hw/virtio/vhost-shadow-virtqueue.c
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+++ b/hw/virtio/vhost-shadow-virtqueue.c
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@@ -509,9 +509,6 @@ size_t vhost_svq_poll(VhostShadowVirtqueue *svq)
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if (unlikely(g_get_monotonic_time() - start_us > 10e6)) {
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return 0;
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}
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-
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- /* Make sure we read new used_idx */
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- smp_rmb();
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} while (true);
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}
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--
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2.31.1
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