[RFC v4 10/11] vhost: Support vduse suspend feature

["Eugenio Pérez" <eperezma@redhat.com>]

Add support for the VDUSE_F_SUSPEND feature.

The suspend feature allows the driver to stop the device from processing
the virtqueues.  This ensures that the virtqueue state can be fetched
reliably in a live migration.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 lib/vhost/vduse.c | 35 ++++++++++++++++++++++++++++++++++-
 lib/vhost/vhost.h |  1 +
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/lib/vhost/vduse.c b/lib/vhost/vduse.c
index cb0bbed96012..7156ec4facd7 100644
--- a/lib/vhost/vduse.c
+++ b/lib/vhost/vduse.c
@@ -46,7 +46,8 @@ static const char * const vduse_reqs_str[] = {
 	(id < RTE_DIM(vduse_reqs_str) ? \
 	vduse_reqs_str[id] : "Unknown")
 
-static const uint64_t supported_vduse_features = RTE_BIT64(VDUSE_F_QUEUE_READY);
+static const uint64_t supported_vduse_features =
+	RTE_BIT64(VDUSE_F_QUEUE_READY) | RTE_BIT64(VDUSE_F_SUSPEND);
 
 static uint64_t vduse_vq_to_group(struct virtio_net *dev, struct vhost_virtqueue *vq)
 {
@@ -412,6 +413,7 @@ vduse_device_stop(struct virtio_net *dev)
 	vhost_destroy_device_notify(dev);
 
 	dev->flags &= ~VIRTIO_DEV_READY;
+	dev->vduse_suspended = false;
 
 	for (i = 0; i < dev->nr_vring; i++)
 		vduse_vring_cleanup(dev, i);
@@ -518,6 +520,12 @@ vduse_events_handler(int fd, void *arg, int *close __rte_unused)
 			resp.result = VDUSE_REQ_RESULT_FAILED;
 			break;
 		}
+		if (dev->vduse_suspended) {
+			VHOST_CONFIG_LOG(dev->ifname, ERR,
+				"SET_VQ_READY received on suspended device");
+			resp.result = VDUSE_REQ_RESULT_FAILED;
+			break;
+		}
 
 		i = req.vq_ready.num;
 		if (i >= dev->nr_vring) {
@@ -548,6 +556,31 @@ vduse_events_handler(int fd, void *arg, int *close __rte_unused)
 		vq->enabled = req.vq_ready.ready;
 		resp.result = VDUSE_REQ_RESULT_OK;
 		break;
+	case VDUSE_SUSPEND:
+		if (!(dev->vduse_features & RTE_BIT64(VDUSE_F_SUSPEND))) {
+			VHOST_CONFIG_LOG(dev->ifname, ERR,
+				"Unnegotiated suspend message");
+			resp.result = VDUSE_REQ_RESULT_FAILED;
+			break;
+		}
+		if (!(dev->status & VIRTIO_DEVICE_STATUS_DRIVER_OK)) {
+			VHOST_CONFIG_LOG(dev->ifname, ERR,
+				"Unexpected suspend message with no DRIVER_OK");
+			resp.result = VDUSE_REQ_RESULT_FAILED;
+			break;
+		}
+		for (i = 0; dev->notify_ops != NULL &&
+			    dev->notify_ops->vring_state_changed != NULL &&
+			    i < dev->nr_vring; i++) {
+			if (dev->virtqueue[i] == dev->cvq)
+				continue;
+
+			dev->notify_ops->vring_state_changed(dev->vid, i, false);
+		}
+		dev->vduse_suspended = true;
+		resp.result = VDUSE_REQ_RESULT_OK;
+		break;
+
 	default:
 		resp.result = VDUSE_REQ_RESULT_FAILED;
 		break;
diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h
index c2b645c2d4b0..f0e7953e3bdc 100644
--- a/lib/vhost/vhost.h
+++ b/lib/vhost/vhost.h
@@ -534,6 +534,7 @@ struct __rte_cache_aligned virtio_net {
 	int			vduse_dev_fd;
 	uint64_t		vduse_api_ver;
 	uint64_t		vduse_features;
+	bool			vduse_suspended;
 
 	struct vhost_virtqueue	*cvq;
 
-- 
2.55.0