vhost-user: add slave-req-fd support (4bbeeba0) · Commits · SUMMER2020 / students / proj-2021291

docs/specs/vhost-user.txt

+30 −2

Original line number	Diff line number	Diff line
		@@ -139,6 +139,7 @@ in the ancillary data:
		* VHOST_USER_SET_VRING_KICK
		* VHOST_USER_SET_VRING_CALL
		* VHOST_USER_SET_VRING_ERR
		* VHOST_USER_SET_SLAVE_REQ_FD

		If Master is unable to send the full message or receives a wrong reply it will
		close the connection. An optional reconnection mechanism can be implemented.
		@@ -252,6 +253,18 @@ Once the source has finished migration, rings will be stopped by
		the source. No further update must be done before rings are
		restarted.

		Slave communication
		-------------------

		An optional communication channel is provided if the slave declares
		VHOST_USER_PROTOCOL_F_SLAVE_REQ protocol feature, to allow the slave to make
		requests to the master.

		The fd is provided via VHOST_USER_SET_SLAVE_REQ_FD ancillary data.

		A slave may then send VHOST_USER_SLAVE_* messages to the master
		using this fd communication channel.

		Protocol features
		-----------------

		@@ -260,9 +273,10 @@ Protocol features
		#define VHOST_USER_PROTOCOL_F_RARP 2
		#define VHOST_USER_PROTOCOL_F_REPLY_ACK 3
		#define VHOST_USER_PROTOCOL_F_MTU 4
		#define VHOST_USER_PROTOCOL_F_SLAVE_REQ 5

		Message types
		-------------
		Master message types
		--------------------

		* VHOST_USER_GET_FEATURES

		@@ -486,6 +500,20 @@ Message types
		If VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated, slave must respond
		with zero in case the specified MTU is valid, or non-zero otherwise.

		* VHOST_USER_SET_SLAVE_REQ_FD

		Id: 21
		Equivalent ioctl: N/A
		Master payload: N/A

		Set the socket file descriptor for slave initiated requests. It is passed
		in the ancillary data.
		This request should be sent only when VHOST_USER_F_PROTOCOL_FEATURES
		has been negotiated, and protocol feature bit VHOST_USER_PROTOCOL_F_SLAVE_REQ
		bit is present in VHOST_USER_GET_PROTOCOL_FEATURES.
		If VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated, slave must respond
		with zero for success, non-zero otherwise.

		VHOST_USER_PROTOCOL_F_REPLY_ACK:
		-------------------------------
		The original vhost-user specification only demands replies for certain

hw/virtio/vhost-user.c

+127 −0

Original line number	Diff line number	Diff line
		@@ -32,6 +32,7 @@ enum VhostUserProtocolFeature {
		VHOST_USER_PROTOCOL_F_RARP = 2,
		VHOST_USER_PROTOCOL_F_REPLY_ACK = 3,
		VHOST_USER_PROTOCOL_F_NET_MTU = 4,
		VHOST_USER_PROTOCOL_F_SLAVE_REQ = 5,

		VHOST_USER_PROTOCOL_F_MAX
		};
		@@ -60,9 +61,15 @@ typedef enum VhostUserRequest {
		VHOST_USER_SET_VRING_ENABLE = 18,
		VHOST_USER_SEND_RARP = 19,
		VHOST_USER_NET_SET_MTU = 20,
		VHOST_USER_SET_SLAVE_REQ_FD = 21,
		VHOST_USER_MAX
		} VhostUserRequest;

		typedef enum VhostUserSlaveRequest {
		VHOST_USER_SLAVE_NONE = 0,
		VHOST_USER_SLAVE_MAX
		} VhostUserSlaveRequest;

		typedef struct VhostUserMemoryRegion {
		uint64_t guest_phys_addr;
		uint64_t memory_size;
		@@ -112,6 +119,7 @@ static VhostUserMsg m __attribute__ ((unused));

		struct vhost_user {
		CharBackend *chr;
		int slave_fd;
		};

		static bool ioeventfd_enabled(void)
		@@ -578,6 +586,115 @@ static int vhost_user_reset_device(struct vhost_dev *dev)
		return 0;
		}

		static void slave_read(void *opaque)
		{
		struct vhost_dev *dev = opaque;
		struct vhost_user *u = dev->opaque;
		VhostUserMsg msg = { 0, };
		int size, ret = 0;

		/* Read header */
		size = read(u->slave_fd, &msg, VHOST_USER_HDR_SIZE);
		if (size != VHOST_USER_HDR_SIZE) {
		error_report("Failed to read from slave.");
		goto err;
		}

		if (msg.size > VHOST_USER_PAYLOAD_SIZE) {
		error_report("Failed to read msg header."
		" Size %d exceeds the maximum %zu.", msg.size,
		VHOST_USER_PAYLOAD_SIZE);
		goto err;
		}

		/* Read payload */
		size = read(u->slave_fd, &msg.payload, msg.size);
		if (size != msg.size) {
		error_report("Failed to read payload from slave.");
		goto err;
		}

		switch (msg.request) {
		default:
		error_report("Received unexpected msg type.");
		ret = -EINVAL;
		}

		/*
		* REPLY_ACK feature handling. Other reply types has to be managed
		* directly in their request handlers.
		*/
		if (msg.flags & VHOST_USER_NEED_REPLY_MASK) {
		msg.flags &= ~VHOST_USER_NEED_REPLY_MASK;
		msg.flags \|= VHOST_USER_REPLY_MASK;

		msg.payload.u64 = !!ret;
		msg.size = sizeof(msg.payload.u64);

		size = write(u->slave_fd, &msg, VHOST_USER_HDR_SIZE + msg.size);
		if (size != VHOST_USER_HDR_SIZE + msg.size) {
		error_report("Failed to send msg reply to slave.");
		goto err;
		}
		}

		return;

		err:
		qemu_set_fd_handler(u->slave_fd, NULL, NULL, NULL);
		close(u->slave_fd);
		u->slave_fd = -1;
		return;
		}

		static int vhost_setup_slave_channel(struct vhost_dev *dev)
		{
		VhostUserMsg msg = {
		.request = VHOST_USER_SET_SLAVE_REQ_FD,
		.flags = VHOST_USER_VERSION,
		};
		struct vhost_user *u = dev->opaque;
		int sv[2], ret = 0;
		bool reply_supported = virtio_has_feature(dev->protocol_features,
		VHOST_USER_PROTOCOL_F_REPLY_ACK);

		if (!virtio_has_feature(dev->protocol_features,
		VHOST_USER_PROTOCOL_F_SLAVE_REQ)) {
		return 0;
		}

		if (socketpair(PF_UNIX, SOCK_STREAM, 0, sv) == -1) {
		error_report("socketpair() failed");
		return -1;
		}

		u->slave_fd = sv[0];
		qemu_set_fd_handler(u->slave_fd, slave_read, NULL, dev);

		if (reply_supported) {
		msg.flags \|= VHOST_USER_NEED_REPLY_MASK;
		}

		ret = vhost_user_write(dev, &msg, &sv[1], 1);
		if (ret) {
		goto out;
		}

		if (reply_supported) {
		ret = process_message_reply(dev, &msg);
		}

		out:
		close(sv[1]);
		if (ret) {
		qemu_set_fd_handler(u->slave_fd, NULL, NULL, NULL);
		close(u->slave_fd);
		u->slave_fd = -1;
		}

		return ret;
		}

		static int vhost_user_init(struct vhost_dev dev, void opaque)
		{
		uint64_t features;
		@@ -588,6 +705,7 @@ static int vhost_user_init(struct vhost_dev dev, void opaque)

		u = g_new0(struct vhost_user, 1);
		u->chr = opaque;
		u->slave_fd = -1;
		dev->opaque = u;

		err = vhost_user_get_features(dev, &features);
		@@ -628,6 +746,11 @@ static int vhost_user_init(struct vhost_dev dev, void opaque)
		"VHOST_USER_PROTOCOL_F_LOG_SHMFD feature.");
		}

		err = vhost_setup_slave_channel(dev);
		if (err < 0) {
		return err;
		}

		return 0;
		}

		@@ -638,6 +761,10 @@ static int vhost_user_cleanup(struct vhost_dev *dev)
		assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);

		u = dev->opaque;
		if (u->slave_fd >= 0) {
		close(u->slave_fd);
		u->slave_fd = -1;
		}
		g_free(u);
		dev->opaque = 0;