Subject: [PATCH v3 8/8] tools/virtio: Make --reset reset ring idx

From: Eugenio Pérez <[email-masked]>
Date: Tue, 31 Mar 2020 21:28:04 +0200

Signed-off-by: Eugenio Pérez <[email-masked]>
---
 drivers/virtio/virtio_ring.c | 29 +++++++++++++++++++++++++++++
 tools/virtio/linux/virtio.h  |  2 ++
 tools/virtio/virtio_test.c   | 28 +++++++++++++++++++++++++++-
 3 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 867c7ebd3f10..01b322ee2e04 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1810,6 +1810,35 @@ int virtqueue_add_inbuf_ctx(struct virtqueue *vq,
 }
 EXPORT_SYMBOL_GPL(virtqueue_add_inbuf_ctx);
 
+#ifndef __KERNEL__
+
+/**
+ * virtqueue_reset_free_head - Reset to 0 the members of split ring.
+ * @vq: Virtqueue to reset.
+ *
+ * At this moment, is only meant for debug the ring index change, do not use
+ * in production.
+ */
+void virtqueue_reset_free_head(struct virtqueue *_vq)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+
+	// vq->last_used_idx = 0;
+	vq->num_added = 0;
+
+	vq->split.queue_size_in_bytes = 0;
+	vq->split.avail_flags_shadow = 0;
+	vq->split.avail_idx_shadow = 0;
+
+	memset(vq->split.desc_state, 0, vq->split.vring.num *
+			sizeof(struct vring_desc_state_split));
+
+	vq->free_head = 0;
+}
+EXPORT_SYMBOL_GPL(virtqueue_reset_free_head);
+
+#endif
+
 /**
  * virtqueue_kick_prepare - first half of split virtqueue_kick call.
  * @_vq: the struct virtqueue
diff --git a/tools/virtio/linux/virtio.h b/tools/virtio/linux/virtio.h
index b751350d4ce8..5d33eab6b814 100644
--- a/tools/virtio/linux/virtio.h
+++ b/tools/virtio/linux/virtio.h
@@ -65,4 +65,6 @@ struct virtqueue *vring_new_virtqueue(unsigned int index,
 				      const char *name);
 void vring_del_virtqueue(struct virtqueue *vq);
 
+void virtqueue_reset_free_head(struct virtqueue *vq);
+
 #endif
diff --git a/tools/virtio/virtio_test.c b/tools/virtio/virtio_test.c
index 93d81cd64ba0..bf21ece30594 100644
--- a/tools/virtio/virtio_test.c
+++ b/tools/virtio/virtio_test.c
@@ -49,6 +49,7 @@ struct vdev_info {
 
 static const struct vhost_vring_file no_backend = { .fd = -1 },
 				     backend = { .fd = 1 };
+static const struct vhost_vring_state null_state = {};
 
 bool vq_notify(struct virtqueue *vq)
 {
@@ -218,10 +219,33 @@ static void run_test(struct vdev_info *dev, struct vq_info *vq,
 			}
 
 			if (reset) {
+				struct vhost_vring_state s = { .index = 0 };
+				int i;
+				vq->vring.avail->idx = 0;
+				vq->vq->num_free = vq->vring.num;
+
+				// Put everything in free lists.
+				for (i = 0; i < vq->vring.num-1; i++)
+					vq->vring.desc[i].next =
+						cpu_to_virtio16(&dev->vdev,
+								i + 1);
+				vq->vring.desc[vq->vring.num-1].next = 0;
+				virtqueue_reset_free_head(vq->vq);
+
+				r = ioctl(dev->control, VHOST_GET_VRING_BASE,
+					  &s);
+				assert(!r);
+
+				s.num = 0;
+				r = ioctl(dev->control, VHOST_SET_VRING_BASE,
+					  &null_state);
+				assert(!r);
+
 				r = ioctl(dev->control, VHOST_TEST_SET_BACKEND,
 					  &backend);
 				assert(!r);
 
+				started = completed;
                                 while (completed > next_reset)
 					next_reset += completed;
 			}
@@ -243,7 +267,9 @@ static void run_test(struct vdev_info *dev, struct vq_info *vq,
 	test = 0;
 	r = ioctl(dev->control, VHOST_TEST_RUN, &test);
 	assert(r >= 0);
-	fprintf(stderr, "spurious wakeups: 0x%llx\n", spurious);
+	fprintf(stderr,
+		"spurious wakeups: 0x%llx started=0x%lx completed=0x%lx\n",
+		spurious, started, completed);
 }
 
 const char optstring[] = "h";
-- 
2.18.1