dm: virtio: add vhost support

This patch adds the vhost support to the device model virtio. A vhost
proxy is implemented based on the virtio framework and vhost char dev.
Key data structures and external interfaces are implemented in this
patch.

Tracked-On: #1329
Signed-off-by: Jian Jun Chen <jian.jun.chen@intel.com>
Acked-by: Yu Wang <yu1.wang@intel.com>

devicemodel/include/vhost.h

@@ -0,0 +1,136 @@
+/*
+ * Copyright (C) 2018 Intel Corporation. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#ifndef __VHOST_H__
+#define __VHOST_H__
+
+#include "virtio.h"
+#include "mevent.h"
+
+struct vhost_vq {
+	int kick_fd;		/**< fd of kick eventfd */
+	int call_fd;		/**< fd of call eventfd */
+	int idx;		/**< index of this vq in vhost dev */
+	struct mevent *mevp;	/**< mevent for call eventfd */
+	struct vhost_dev *dev;	/**< pointer to vhost_dev */
+};
+
+struct vhost_dev {
+	/**
+	 * backpointer to virtio_base
+	 */
+	struct virtio_base *base;
+
+	/**
+	 * pointer to vhost_vq array
+	 */
+	struct vhost_vq *vqs;
+
+	/**
+	 * number of virtqueues
+	 */
+	int nvqs;
+
+	/**
+	 * vhost chardev fd
+	 */
+	int fd;
+
+	/**
+	 * first vq's index in virtio_vq_info
+	 */
+	int vq_idx;
+
+	/**
+	 * supported virtio defined features
+	 */
+	uint64_t vhost_features;
+
+	/**
+	 * vhost self-defined internal features bits used for
+	 * communicate between vhost user-space and kernel-space modules
+	 */
+	uint64_t vhost_ext_features;
+
+	/**
+	 * vq busyloop timeout in us
+	 */
+	uint32_t busyloop_timeout;
+
+	/**
+	 * whether vhost is started
+	 */
+	bool started;
+};
+
+/**
+ * @brief vhost_dev initialization.
+ *
+ * This interface is called to initialize the vhost_dev. It must be called
+ * before the actual feature negoitiation with the guest OS starts.
+ *
+ * @param vdev Pointer to struct vhost_dev.
+ * @param base Pointer to struct virtio_base.
+ * @param fd fd of the vhost chardev.
+ * @param vq_idx The first virtqueue which would be used by this vhost dev.
+ * @param vhost_features Subset of vhost features which would be enabled.
+ * @param vhost_ext_features Specific vhost internal features to be enabled.
+ * @param busyloop_timeout Busy loop timeout in us.
+ *
+ * @return 0 on success and -1 on failure.
+ */
+int vhost_dev_init(struct vhost_dev *vdev, struct virtio_base *base, int fd,
+		   int vq_idx, uint64_t vhost_features,
+		   uint64_t vhost_ext_features, uint32_t busyloop_timeout);
+
+/**
+ * @brief vhost_dev cleanup.
+ *
+ * This interface is called to cleanup the vhost_dev.
+ *
+ * @param vdev Pointer to struct vhost_dev.
+ *
+ * @return 0 on success and -1 on failure.
+ */
+int vhost_dev_deinit(struct vhost_dev *vdev);
+
+/**
+ * @brief start vhost data plane.
+ *
+ * This interface is called to start the data plane in vhost.
+ *
+ * @param vdev Pointer to struct vhost_dev.
+ *
+ * @return 0 on success and -1 on failure.
+ */
+int vhost_dev_start(struct vhost_dev *vdev);
+
+/**
+ * @brief stop vhost data plane.
+ *
+ * This interface is called to stop the data plane in vhost.
+ *
+ * @param vdev Pointer to struct vhost_dev.
+ *
+ * @return 0 on success and -1 on failure.
+ */
+int vhost_dev_stop(struct vhost_dev *vdev);
+
+/**
+ * @brief set backend fd of vhost net.
+ *
+ * This interface is called to set the backend fd (for example tap fd)
+ * to vhost.
+ *
+ * @param vdev Pointer to struct vhost_dev.
+ * @param backend_fd fd of backend (for example tap fd).
+ *
+ * @return 0 on success and -1 on failure.
+ */
+int vhost_net_set_backend(struct vhost_dev *vdev, int backend_fd);
+
+#endif