[dpdk-dev] [RFC 01/24] vhost: move vring_call() into trans_af_unix.c

[Stefan Hajnoczi]

File descriptor passing is specific to the AF_UNIX vhost-user protocol
transport.  In order to add support for additional transports it is
necessary to extract transport-specific code from the main vhost-user
code.

This patch introduces struct vhost_transport_ops and associates each
device with a transport.  Core vhost-user code calls into
vhost_transport_ops to perform transport-specific operations.

Notifying callfd is a transport-specific operation so it belongs in
trans_af_unix.c.

Several more patches follow this one to complete the task of moving
AF_UNIX transport code out of core vhost-user code.

Signed-off-by: Stefan Hajnoczi <stefanha at redhat.com>
---
 lib/librte_vhost/Makefile        |  2 +-
 lib/librte_vhost/vhost.h         | 35 +++++++++++++++++++++++-----
 lib/librte_vhost/trans_af_unix.c | 49 ++++++++++++++++++++++++++++++++++++++++
 lib/librte_vhost/vhost.c         |  1 +
 4 files changed, 80 insertions(+), 7 deletions(-)
 create mode 100644 lib/librte_vhost/trans_af_unix.c

diff --git a/lib/librte_vhost/Makefile b/lib/librte_vhost/Makefile
index 065d5c469..ccbbce3af 100644
--- a/lib/librte_vhost/Makefile
+++ b/lib/librte_vhost/Makefile
@@ -21,7 +21,7 @@ LDLIBS += -lrte_eal -lrte_mempool -lrte_mbuf -lrte_ethdev -lrte_net
 
 # all source are stored in SRCS-y
 SRCS-$(CONFIG_RTE_LIBRTE_VHOST) := fd_man.c iotlb.c socket.c vhost.c \
-					vhost_user.c virtio_net.c
+					vhost_user.c virtio_net.c trans_af_unix.c
 
 # install includes
 SYMLINK-$(CONFIG_RTE_LIBRTE_VHOST)-include += rte_vhost.h
diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index b2bf0e833..53811a8b1 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -200,6 +200,30 @@ struct guest_page {
 	uint64_t size;
 };
 
+struct virtio_net;
+
+/**
+ * A structure containing function pointers for transport-specific operations.
+ */
+struct vhost_transport_ops {
+	/**
+	 * Notify the guest that used descriptors have been added to the vring.
+	 * The VRING_AVAIL_F_NO_INTERRUPT flag has already been checked so this
+	 * function just needs to perform the notification.
+	 *
+	 * @param dev
+	 *  vhost device
+	 * @param vq
+	 *  vhost virtqueue
+	 * @return
+	 *  0 on success, -1 on failure
+	 */
+	int (*vring_call)(struct virtio_net *dev, struct vhost_virtqueue *vq);
+};
+
+/** The traditional AF_UNIX vhost-user protocol transport. */
+extern const struct vhost_transport_ops af_unix_trans_ops;
+
 /**
  * Device structure contains all configuration information relating
  * to the device.
@@ -226,6 +250,7 @@ struct virtio_net {
 	uint16_t		mtu;
 
 	struct vhost_device_ops const *notify_ops;
+	struct vhost_transport_ops const *trans_ops;
 
 	uint32_t		nr_guest_pages;
 	uint32_t		max_guest_pages;
@@ -405,16 +430,14 @@ vhost_vring_call(struct virtio_net *dev, struct vhost_virtqueue *vq)
 			__func__,
 			vhost_used_event(vq),
 			old, new);
-		if (vhost_need_event(vhost_used_event(vq), new, old)
-			&& (vq->callfd >= 0)) {
+		if (vhost_need_event(vhost_used_event(vq), new, old)) {
 			vq->signalled_used = vq->last_used_idx;
-			eventfd_write(vq->callfd, (eventfd_t) 1);
+			dev->trans_ops->vring_call(dev, vq);
 		}
 	} else {
 		/* Kick the guest if necessary. */
-		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
-				&& (vq->callfd >= 0))
-			eventfd_write(vq->callfd, (eventfd_t)1);
+		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
+			dev->trans_ops->vring_call(dev, vq);
 	}
 }
 
diff --git a/lib/librte_vhost/trans_af_unix.c b/lib/librte_vhost/trans_af_unix.c
new file mode 100644
index 000000000..9ed04b7eb
--- /dev/null
+++ b/lib/librte_vhost/trans_af_unix.c
@@ -0,0 +1,49 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2010-2016 Intel Corporation. All rights reserved.
+ *   All rights reserved.
+ *
+ *   Copyright (C) 2017 Red Hat, Inc.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in
+ *       the documentation and/or other materials provided with the
+ *       distribution.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "vhost.h"
+
+static int
+af_unix_vring_call(struct virtio_net *dev __rte_unused,
+		   struct vhost_virtqueue *vq)
+{
+	if (vq->callfd >= 0)
+		eventfd_write(vq->callfd, (eventfd_t)1);
+	return 0;
+}
+
+const struct vhost_transport_ops af_unix_trans_ops = {
+	.vring_call = af_unix_vring_call,
+};
diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index 6789ccce5..630dbd014 100644
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -287,6 +287,7 @@ vhost_new_device(void)
 	vhost_devices[i] = dev;
 	dev->vid = i;
 	dev->slave_req_fd = -1;
+	dev->trans_ops = &af_unix_trans_ops;
 
 	return i;
 }
-- 
2.14.3