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From 0ab3da1092362470d256b433c546bd365d34f930 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: Thu, 21 Jul 2022 15:38:55 +0200
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Subject: [PATCH 19/32] vhost: add vhost_svq_poll
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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: 108: Net Control Virtqueue shadow Support
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RH-Commit: [19/27] 6807bb0bb6e5183b46a03b12b4027c7d767e8555 (eperezmartin/qemu-kvm)
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RH-Bugzilla: 1939363
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RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>
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RH-Acked-by: Cindy Lu <lulu@redhat.com>
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RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
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Bugzilla: https://bugzilla.redhat.com/1939363
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Upstream Status: git://git.qemu.org/qemu.git
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commit 3f44d13dda83d390cc9563e56e7d337e4f6223f4
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Author: Eugenio Pérez <eperezma@redhat.com>
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Date: Wed Jul 20 08:59:38 2022 +0200
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vhost: add vhost_svq_poll
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It allows the Shadow Control VirtQueue to wait for the device to use the
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available buffers.
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Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
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Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
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Signed-off-by: Jason Wang <jasowang@redhat.com>
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Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
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---
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hw/virtio/vhost-shadow-virtqueue.c | 27 +++++++++++++++++++++++++++
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hw/virtio/vhost-shadow-virtqueue.h | 1 +
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2 files changed, 28 insertions(+)
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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 cb879e7b88..95d0d7a7ee 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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@@ -485,6 +485,33 @@ static void vhost_svq_flush(VhostShadowVirtqueue *svq,
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} while (!vhost_svq_enable_notification(svq));
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}
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+/**
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+ * Poll the SVQ for one device used buffer.
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+ *
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+ * This function race with main event loop SVQ polling, so extra
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+ * synchronization is needed.
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+ *
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+ * Return the length written by the device.
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+ */
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+size_t vhost_svq_poll(VhostShadowVirtqueue *svq)
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+{
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+ int64_t start_us = g_get_monotonic_time();
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+ do {
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+ uint32_t len;
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+ VirtQueueElement *elem = vhost_svq_get_buf(svq, &len;;
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+ if (elem) {
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+ return len;
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+ }
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+
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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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/**
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* Forward used buffers.
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*
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diff --git a/hw/virtio/vhost-shadow-virtqueue.h b/hw/virtio/vhost-shadow-virtqueue.h
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index dd78f4bec2..cf442f7dea 100644
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--- a/hw/virtio/vhost-shadow-virtqueue.h
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+++ b/hw/virtio/vhost-shadow-virtqueue.h
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@@ -89,6 +89,7 @@ void vhost_svq_push_elem(VhostShadowVirtqueue *svq,
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int vhost_svq_add(VhostShadowVirtqueue *svq, const struct iovec *out_sg,
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size_t out_num, const struct iovec *in_sg, size_t in_num,
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VirtQueueElement *elem);
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+size_t vhost_svq_poll(VhostShadowVirtqueue *svq);
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void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue *svq, int svq_kick_fd);
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void vhost_svq_set_svq_call_fd(VhostShadowVirtqueue *svq, int call_fd);
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--
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2.31.1
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