text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * Virtio vhost-user driver
   *
   * Copyright(c) 2019 Intel Corporation
   *
   * This driver allows virtio devices to be used over a vhost-user socket.
   *
   * Guest devices can be instantiated by kernel module or command line
   * parameters. One device will be created for each parameter. Syntax:
   *
   *		virtio_uml.device=<socket>:<virtio_id>[:<platform_id>]
   * where:
   *		<socket>	:= vhost-user socket path to connect
   *		<virtio_id>	:= virtio device id (as in virtio_ids.h)
   *		<platform_id>	:= (optional) platform device id
   *
   * example:
   *		virtio_uml.device=/var/uml.socket:1
   *
   * Based on Virtio MMIO driver by Pawel Moll, copyright 2011-2014, ARM Ltd.
   */
  #include <linux/module.h>
  #include <linux/platform_device.h>
  #include <linux/slab.h>
  #include <linux/virtio.h>
  #include <linux/virtio_config.h>
  #include <linux/virtio_ring.h>
  #include <linux/time-internal.h>
  #include <shared/as-layout.h>
  #include <irq_kern.h>
  #include <init.h>
  #include <os.h>
  #include "vhost_user.h"
  
  /* Workaround due to a conflict between irq_user.h and irqreturn.h */
  #ifdef IRQ_NONE
  #undef IRQ_NONE
  #endif
  
  #define MAX_SUPPORTED_QUEUE_SIZE	256
  
  #define to_virtio_uml_device(_vdev) \
  	container_of(_vdev, struct virtio_uml_device, vdev)
  
  struct virtio_uml_platform_data {
  	u32 virtio_device_id;
  	const char *socket_path;
  	struct work_struct conn_broken_wk;
  	struct platform_device *pdev;
  };
  
  struct virtio_uml_device {
  	struct virtio_device vdev;
  	struct platform_device *pdev;
  
  	spinlock_t sock_lock;
  	int sock, req_fd;
  	u64 features;
  	u64 protocol_features;
  	u8 status;
  	u8 registered:1;
  };
  
  struct virtio_uml_vq_info {
  	int kick_fd, call_fd;
  	char name[32];
  #ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
  	struct virtqueue *vq;
  	vq_callback_t *callback;
  	struct time_travel_event defer;
  #endif
  };
  
  extern unsigned long long physmem_size, highmem;
  
  #define vu_err(vu_dev, ...)	dev_err(&(vu_dev)->pdev->dev, ##__VA_ARGS__)
  
  /* Vhost-user protocol */
  
  static int full_sendmsg_fds(int fd, const void *buf, unsigned int len,
  			    const int *fds, unsigned int fds_num)
  {
  	int rc;
  
  	do {
  		rc = os_sendmsg_fds(fd, buf, len, fds, fds_num);
  		if (rc > 0) {
  			buf += rc;
  			len -= rc;
  			fds = NULL;
  			fds_num = 0;
  		}
  	} while (len && (rc >= 0 || rc == -EINTR));
  
  	if (rc < 0)
  		return rc;
  	return 0;
  }
  
  static int full_read(int fd, void *buf, int len, bool abortable)
  {
  	int rc;
  
  	do {
  		rc = os_read_file(fd, buf, len);
  		if (rc > 0) {
  			buf += rc;
  			len -= rc;
  		}
  	} while (len && (rc > 0 || rc == -EINTR || (!abortable && rc == -EAGAIN)));
  
  	if (rc < 0)
  		return rc;
  	if (rc == 0)
  		return -ECONNRESET;
  	return 0;
  }
  
  static int vhost_user_recv_header(int fd, struct vhost_user_msg *msg)
  {
  	return full_read(fd, msg, sizeof(msg->header), true);
  }
  
  static int vhost_user_recv(struct virtio_uml_device *vu_dev,
  			   int fd, struct vhost_user_msg *msg,
  			   size_t max_payload_size, bool wait)
  {
  	size_t size;
  	int rc;
  
  	/*
  	 * In virtio time-travel mode, we're handling all the vhost-user
  	 * FDs by polling them whenever appropriate. However, we may get
  	 * into a situation where we're sending out an interrupt message
  	 * to a device (e.g. a net device) and need to handle a simulation
  	 * time message while doing so, e.g. one that tells us to update
  	 * our idea of how long we can run without scheduling.
  	 *
  	 * Thus, we need to not just read() from the given fd, but need
  	 * to also handle messages for the simulation time - this function
  	 * does that for us while waiting for the given fd to be readable.
  	 */
  	if (wait)
  		time_travel_wait_readable(fd);
  
  	rc = vhost_user_recv_header(fd, msg);
  
  	if (rc == -ECONNRESET && vu_dev->registered) {
  		struct virtio_uml_platform_data *pdata;
  
  		pdata = vu_dev->pdev->dev.platform_data;
  
  		virtio_break_device(&vu_dev->vdev);
  		schedule_work(&pdata->conn_broken_wk);
  	}
  	if (rc)
  		return rc;
  	size = msg->header.size;
  	if (size > max_payload_size)
  		return -EPROTO;
  	return full_read(fd, &msg->payload, size, false);
  }
  
  static int vhost_user_recv_resp(struct virtio_uml_device *vu_dev,
  				struct vhost_user_msg *msg,
  				size_t max_payload_size)
  {
  	int rc = vhost_user_recv(vu_dev, vu_dev->sock, msg,
  				 max_payload_size, true);
  
  	if (rc)
  		return rc;
  
  	if (msg->header.flags != (VHOST_USER_FLAG_REPLY | VHOST_USER_VERSION))
  		return -EPROTO;
  
  	return 0;
  }
  
  static int vhost_user_recv_u64(struct virtio_uml_device *vu_dev,
  			       u64 *value)
  {
  	struct vhost_user_msg msg;
  	int rc = vhost_user_recv_resp(vu_dev, &msg,
  				      sizeof(msg.payload.integer));
  
  	if (rc)
  		return rc;
  	if (msg.header.size != sizeof(msg.payload.integer))
  		return -EPROTO;
  	*value = msg.payload.integer;
  	return 0;
  }
  
  static int vhost_user_recv_req(struct virtio_uml_device *vu_dev,
  			       struct vhost_user_msg *msg,
  			       size_t max_payload_size)
  {
  	int rc = vhost_user_recv(vu_dev, vu_dev->req_fd, msg,
  				 max_payload_size, false);
  
  	if (rc)
  		return rc;
  
  	if ((msg->header.flags & ~VHOST_USER_FLAG_NEED_REPLY) !=
  			VHOST_USER_VERSION)
  		return -EPROTO;
  
  	return 0;
  }
  
  static int vhost_user_send(struct virtio_uml_device *vu_dev,
  			   bool need_response, struct vhost_user_msg *msg,
  			   int *fds, size_t num_fds)
  {
  	size_t size = sizeof(msg->header) + msg->header.size;
  	unsigned long flags;
  	bool request_ack;
  	int rc;
  
  	msg->header.flags |= VHOST_USER_VERSION;
  
  	/*
  	 * The need_response flag indicates that we already need a response,
  	 * e.g. to read the features. In these cases, don't request an ACK as
  	 * it is meaningless. Also request an ACK only if supported.
  	 */
  	request_ack = !need_response;
  	if (!(vu_dev->protocol_features &
  			BIT_ULL(VHOST_USER_PROTOCOL_F_REPLY_ACK)))
  		request_ack = false;
  
  	if (request_ack)
  		msg->header.flags |= VHOST_USER_FLAG_NEED_REPLY;
  
  	spin_lock_irqsave(&vu_dev->sock_lock, flags);
  	rc = full_sendmsg_fds(vu_dev->sock, msg, size, fds, num_fds);
  	if (rc < 0)
  		goto out;
  
  	if (request_ack) {
  		uint64_t status;
  
  		rc = vhost_user_recv_u64(vu_dev, &status);
  		if (rc)
  			goto out;
  
  		if (status) {
  			vu_err(vu_dev, "slave reports error: %llu\n", status);
  			rc = -EIO;
  			goto out;
  		}
  	}
  
  out:
  	spin_unlock_irqrestore(&vu_dev->sock_lock, flags);
  	return rc;
  }
  
  static int vhost_user_send_no_payload(struct virtio_uml_device *vu_dev,
  				      bool need_response, u32 request)
  {
  	struct vhost_user_msg msg = {
  		.header.request = request,
  	};
  
  	return vhost_user_send(vu_dev, need_response, &msg, NULL, 0);
  }
  
  static int vhost_user_send_no_payload_fd(struct virtio_uml_device *vu_dev,
  					 u32 request, int fd)
  {
  	struct vhost_user_msg msg = {
  		.header.request = request,
  	};
  
  	return vhost_user_send(vu_dev, false, &msg, &fd, 1);
  }
  
  static int vhost_user_send_u64(struct virtio_uml_device *vu_dev,
  			       u32 request, u64 value)
  {
  	struct vhost_user_msg msg = {
  		.header.request = request,
  		.header.size = sizeof(msg.payload.integer),
  		.payload.integer = value,
  	};
  
  	return vhost_user_send(vu_dev, false, &msg, NULL, 0);
  }
  
  static int vhost_user_set_owner(struct virtio_uml_device *vu_dev)
  {
  	return vhost_user_send_no_payload(vu_dev, false, VHOST_USER_SET_OWNER);
  }
  
  static int vhost_user_get_features(struct virtio_uml_device *vu_dev,
  				   u64 *features)
  {
  	int rc = vhost_user_send_no_payload(vu_dev, true,
  					    VHOST_USER_GET_FEATURES);
  
  	if (rc)
  		return rc;
  	return vhost_user_recv_u64(vu_dev, features);
  }
  
  static int vhost_user_set_features(struct virtio_uml_device *vu_dev,
  				   u64 features)
  {
  	return vhost_user_send_u64(vu_dev, VHOST_USER_SET_FEATURES, features);
  }
  
  static int vhost_user_get_protocol_features(struct virtio_uml_device *vu_dev,
  					    u64 *protocol_features)
  {
  	int rc = vhost_user_send_no_payload(vu_dev, true,
  			VHOST_USER_GET_PROTOCOL_FEATURES);
  
  	if (rc)
  		return rc;
  	return vhost_user_recv_u64(vu_dev, protocol_features);
  }
  
  static int vhost_user_set_protocol_features(struct virtio_uml_device *vu_dev,
  					    u64 protocol_features)
  {
  	return vhost_user_send_u64(vu_dev, VHOST_USER_SET_PROTOCOL_FEATURES,
  				   protocol_features);
  }
  
  static void vhost_user_reply(struct virtio_uml_device *vu_dev,
  			     struct vhost_user_msg *msg, int response)
  {
  	struct vhost_user_msg reply = {
  		.payload.integer = response,
  	};
  	size_t size = sizeof(reply.header) + sizeof(reply.payload.integer);
  	int rc;
  
  	reply.header = msg->header;
  	reply.header.flags &= ~VHOST_USER_FLAG_NEED_REPLY;
  	reply.header.flags |= VHOST_USER_FLAG_REPLY;
  	reply.header.size = sizeof(reply.payload.integer);
  
  	rc = full_sendmsg_fds(vu_dev->req_fd, &reply, size, NULL, 0);
  
  	if (rc)
  		vu_err(vu_dev,
  		       "sending reply to slave request failed: %d (size %zu)\n",
  		       rc, size);
  }
  
  static irqreturn_t vu_req_interrupt(int irq, void *data)
  {
  	struct virtio_uml_device *vu_dev = data;
  	struct virtqueue *vq;
  	int response = 1;
  	struct {
  		struct vhost_user_msg msg;
  		u8 extra_payload[512];
  	} msg;
  	int rc;
  
  	rc = vhost_user_recv_req(vu_dev, &msg.msg,
  				 sizeof(msg.msg.payload) +
  				 sizeof(msg.extra_payload));
  
  	if (rc)
  		return IRQ_NONE;
  
  	switch (msg.msg.header.request) {
  	case VHOST_USER_SLAVE_CONFIG_CHANGE_MSG:
  		virtio_config_changed(&vu_dev->vdev);
  		response = 0;
  		break;
  	case VHOST_USER_SLAVE_VRING_CALL:
  		virtio_device_for_each_vq((&vu_dev->vdev), vq) {
  			if (vq->index == msg.msg.payload.vring_state.index) {
  				response = 0;
  				vring_interrupt(0 /* ignored */, vq);
  				break;
  			}
  		}
  		break;
  	case VHOST_USER_SLAVE_IOTLB_MSG:
  		/* not supported - VIRTIO_F_IOMMU_PLATFORM */
  	case VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG:
  		/* not supported - VHOST_USER_PROTOCOL_F_HOST_NOTIFIER */
  	default:
  		vu_err(vu_dev, "unexpected slave request %d\n",
  		       msg.msg.header.request);
  	}
  
  	if (msg.msg.header.flags & VHOST_USER_FLAG_NEED_REPLY)
  		vhost_user_reply(vu_dev, &msg.msg, response);
  
  	return IRQ_HANDLED;
  }
  
  static int vhost_user_init_slave_req(struct virtio_uml_device *vu_dev)
  {
  	int rc, req_fds[2];
  
  	/* Use a pipe for slave req fd, SIGIO is not supported for eventfd */
  	rc = os_pipe(req_fds, true, true);
  	if (rc < 0)
  		return rc;
  	vu_dev->req_fd = req_fds[0];
  
  	rc = um_request_irq(VIRTIO_IRQ, vu_dev->req_fd, IRQ_READ,
  			    vu_req_interrupt, IRQF_SHARED,
  			    vu_dev->pdev->name, vu_dev);
  	if (rc)
  		goto err_close;
  
  	rc = vhost_user_send_no_payload_fd(vu_dev, VHOST_USER_SET_SLAVE_REQ_FD,
  					   req_fds[1]);
  	if (rc)
  		goto err_free_irq;
  
  	goto out;
  
  err_free_irq:
  	um_free_irq(VIRTIO_IRQ, vu_dev);
  err_close:
  	os_close_file(req_fds[0]);
  out:
  	/* Close unused write end of request fds */
  	os_close_file(req_fds[1]);
  	return rc;
  }
  
  static int vhost_user_init(struct virtio_uml_device *vu_dev)
  {
  	int rc = vhost_user_set_owner(vu_dev);
  
  	if (rc)
  		return rc;
  	rc = vhost_user_get_features(vu_dev, &vu_dev->features);
  	if (rc)
  		return rc;
  
  	if (vu_dev->features & BIT_ULL(VHOST_USER_F_PROTOCOL_FEATURES)) {
  		rc = vhost_user_get_protocol_features(vu_dev,
  				&vu_dev->protocol_features);
  		if (rc)
  			return rc;
  		vu_dev->protocol_features &= VHOST_USER_SUPPORTED_PROTOCOL_F;
  		rc = vhost_user_set_protocol_features(vu_dev,
  				vu_dev->protocol_features);
  		if (rc)
  			return rc;
  	}
  
  	if (vu_dev->protocol_features &
  			BIT_ULL(VHOST_USER_PROTOCOL_F_SLAVE_REQ)) {
  		rc = vhost_user_init_slave_req(vu_dev);
  		if (rc)
  			return rc;
  	}
  
  	return 0;
  }
  
  static void vhost_user_get_config(struct virtio_uml_device *vu_dev,
  				  u32 offset, void *buf, u32 len)
  {
  	u32 cfg_size = offset + len;
  	struct vhost_user_msg *msg;
  	size_t payload_size = sizeof(msg->payload.config) + cfg_size;
  	size_t msg_size = sizeof(msg->header) + payload_size;
  	int rc;
  
  	if (!(vu_dev->protocol_features &
  	      BIT_ULL(VHOST_USER_PROTOCOL_F_CONFIG)))
  		return;
  
  	msg = kzalloc(msg_size, GFP_KERNEL);
  	if (!msg)
  		return;
  	msg->header.request = VHOST_USER_GET_CONFIG;
  	msg->header.size = payload_size;
  	msg->payload.config.offset = 0;
  	msg->payload.config.size = cfg_size;
  
  	rc = vhost_user_send(vu_dev, true, msg, NULL, 0);
  	if (rc) {
  		vu_err(vu_dev, "sending VHOST_USER_GET_CONFIG failed: %d\n",
  		       rc);
  		goto free;
  	}
  
  	rc = vhost_user_recv_resp(vu_dev, msg, msg_size);
  	if (rc) {
  		vu_err(vu_dev,
  		       "receiving VHOST_USER_GET_CONFIG response failed: %d\n",
  		       rc);
  		goto free;
  	}
  
  	if (msg->header.size != payload_size ||
  	    msg->payload.config.size != cfg_size) {
  		rc = -EPROTO;
  		vu_err(vu_dev,
  		       "Invalid VHOST_USER_GET_CONFIG sizes (payload %d expected %zu, config %u expected %u)\n",
  		       msg->header.size, payload_size,
  		       msg->payload.config.size, cfg_size);
  		goto free;
  	}
  	memcpy(buf, msg->payload.config.payload + offset, len);
  
  free:
  	kfree(msg);
  }
  
  static void vhost_user_set_config(struct virtio_uml_device *vu_dev,
  				  u32 offset, const void *buf, u32 len)
  {
  	struct vhost_user_msg *msg;
  	size_t payload_size = sizeof(msg->payload.config) + len;
  	size_t msg_size = sizeof(msg->header) + payload_size;
  	int rc;
  
  	if (!(vu_dev->protocol_features &
  	      BIT_ULL(VHOST_USER_PROTOCOL_F_CONFIG)))
  		return;
  
  	msg = kzalloc(msg_size, GFP_KERNEL);
  	if (!msg)
  		return;
  	msg->header.request = VHOST_USER_SET_CONFIG;
  	msg->header.size = payload_size;
  	msg->payload.config.offset = offset;
  	msg->payload.config.size = len;
  	memcpy(msg->payload.config.payload, buf, len);
  
  	rc = vhost_user_send(vu_dev, false, msg, NULL, 0);
  	if (rc)
  		vu_err(vu_dev, "sending VHOST_USER_SET_CONFIG failed: %d\n",
  		       rc);
  
  	kfree(msg);
  }
  
  static int vhost_user_init_mem_region(u64 addr, u64 size, int *fd_out,
  				      struct vhost_user_mem_region *region_out)
  {
  	unsigned long long mem_offset;
  	int rc = phys_mapping(addr, &mem_offset);
  
  	if (WARN(rc < 0, "phys_mapping of 0x%llx returned %d\n", addr, rc))
  		return -EFAULT;
  	*fd_out = rc;
  	region_out->guest_addr = addr;
  	region_out->user_addr = addr;
  	region_out->size = size;
  	region_out->mmap_offset = mem_offset;
  
  	/* Ensure mapping is valid for the entire region */
  	rc = phys_mapping(addr + size - 1, &mem_offset);
  	if (WARN(rc != *fd_out, "phys_mapping of 0x%llx failed: %d != %d\n",
  		 addr + size - 1, rc, *fd_out))
  		return -EFAULT;
  	return 0;
  }
  
  static int vhost_user_set_mem_table(struct virtio_uml_device *vu_dev)
  {
  	struct vhost_user_msg msg = {
  		.header.request = VHOST_USER_SET_MEM_TABLE,
  		.header.size = sizeof(msg.payload.mem_regions),
  		.payload.mem_regions.num = 1,
  	};
  	unsigned long reserved = uml_reserved - uml_physmem;
  	int fds[2];
  	int rc;
  
  	/*
  	 * This is a bit tricky, see also the comment with setup_physmem().
  	 *
  	 * Essentially, setup_physmem() uses a file to mmap() our physmem,
  	 * but the code and data we *already* have is omitted. To us, this
  	 * is no difference, since they both become part of our address
  	 * space and memory consumption. To somebody looking in from the
  	 * outside, however, it is different because the part of our memory
  	 * consumption that's already part of the binary (code/data) is not
  	 * mapped from the file, so it's not visible to another mmap from
  	 * the file descriptor.
  	 *
  	 * Thus, don't advertise this space to the vhost-user slave. This
  	 * means that the slave will likely abort or similar when we give
  	 * it an address from the hidden range, since it's not marked as
  	 * a valid address, but at least that way we detect the issue and
  	 * don't just have the slave read an all-zeroes buffer from the
  	 * shared memory file, or write something there that we can never
  	 * see (depending on the direction of the virtqueue traffic.)
  	 *
  	 * Since we usually don't want to use .text for virtio buffers,
  	 * this effectively means that you cannot use
  	 *  1) global variables, which are in the .bss and not in the shm
  	 *     file-backed memory
  	 *  2) the stack in some processes, depending on where they have
  	 *     their stack (or maybe only no interrupt stack?)
  	 *
  	 * The stack is already not typically valid for DMA, so this isn't
  	 * much of a restriction, but global variables might be encountered.
  	 *
  	 * It might be possible to fix it by copying around the data that's
  	 * between bss_start and where we map the file now, but it's not
  	 * something that you typically encounter with virtio drivers, so
  	 * it didn't seem worthwhile.
  	 */
  	rc = vhost_user_init_mem_region(reserved, physmem_size - reserved,
  					&fds[0],
  					&msg.payload.mem_regions.regions[0]);
  
  	if (rc < 0)
  		return rc;
  	if (highmem) {
  		msg.payload.mem_regions.num++;
  		rc = vhost_user_init_mem_region(__pa(end_iomem), highmem,
  				&fds[1], &msg.payload.mem_regions.regions[1]);
  		if (rc < 0)
  			return rc;
  	}
  
  	return vhost_user_send(vu_dev, false, &msg, fds,
  			       msg.payload.mem_regions.num);
  }
  
  static int vhost_user_set_vring_state(struct virtio_uml_device *vu_dev,
  				      u32 request, u32 index, u32 num)
  {
  	struct vhost_user_msg msg = {
  		.header.request = request,
  		.header.size = sizeof(msg.payload.vring_state),
  		.payload.vring_state.index = index,
  		.payload.vring_state.num = num,
  	};
  
  	return vhost_user_send(vu_dev, false, &msg, NULL, 0);
  }
  
  static int vhost_user_set_vring_num(struct virtio_uml_device *vu_dev,
  				    u32 index, u32 num)
  {
  	return vhost_user_set_vring_state(vu_dev, VHOST_USER_SET_VRING_NUM,
  					  index, num);
  }
  
  static int vhost_user_set_vring_base(struct virtio_uml_device *vu_dev,
  				     u32 index, u32 offset)
  {
  	return vhost_user_set_vring_state(vu_dev, VHOST_USER_SET_VRING_BASE,
  					  index, offset);
  }
  
  static int vhost_user_set_vring_addr(struct virtio_uml_device *vu_dev,
  				     u32 index, u64 desc, u64 used, u64 avail,
  				     u64 log)
  {
  	struct vhost_user_msg msg = {
  		.header.request = VHOST_USER_SET_VRING_ADDR,
  		.header.size = sizeof(msg.payload.vring_addr),
  		.payload.vring_addr.index = index,
  		.payload.vring_addr.desc = desc,
  		.payload.vring_addr.used = used,
  		.payload.vring_addr.avail = avail,
  		.payload.vring_addr.log = log,
  	};
  
  	return vhost_user_send(vu_dev, false, &msg, NULL, 0);
  }
  
  static int vhost_user_set_vring_fd(struct virtio_uml_device *vu_dev,
  				   u32 request, int index, int fd)
  {
  	struct vhost_user_msg msg = {
  		.header.request = request,
  		.header.size = sizeof(msg.payload.integer),
  		.payload.integer = index,
  	};
  
  	if (index & ~VHOST_USER_VRING_INDEX_MASK)
  		return -EINVAL;
  	if (fd < 0) {
  		msg.payload.integer |= VHOST_USER_VRING_POLL_MASK;
  		return vhost_user_send(vu_dev, false, &msg, NULL, 0);
  	}
  	return vhost_user_send(vu_dev, false, &msg, &fd, 1);
  }
  
  static int vhost_user_set_vring_call(struct virtio_uml_device *vu_dev,
  				     int index, int fd)
  {
  	return vhost_user_set_vring_fd(vu_dev, VHOST_USER_SET_VRING_CALL,
  				       index, fd);
  }
  
  static int vhost_user_set_vring_kick(struct virtio_uml_device *vu_dev,
  				     int index, int fd)
  {
  	return vhost_user_set_vring_fd(vu_dev, VHOST_USER_SET_VRING_KICK,
  				       index, fd);
  }
  
  static int vhost_user_set_vring_enable(struct virtio_uml_device *vu_dev,
  				       u32 index, bool enable)
  {
  	if (!(vu_dev->features & BIT_ULL(VHOST_USER_F_PROTOCOL_FEATURES)))
  		return 0;
  
  	return vhost_user_set_vring_state(vu_dev, VHOST_USER_SET_VRING_ENABLE,
  					  index, enable);
  }
  
  
  /* Virtio interface */
  
  static bool vu_notify(struct virtqueue *vq)
  {
  	struct virtio_uml_vq_info *info = vq->priv;
  	const uint64_t n = 1;
  	int rc;
  
  	time_travel_propagate_time();
  
  	if (info->kick_fd < 0) {
  		struct virtio_uml_device *vu_dev;
  
  		vu_dev = to_virtio_uml_device(vq->vdev);
  
  		return vhost_user_set_vring_state(vu_dev, VHOST_USER_VRING_KICK,
  						  vq->index, 0) == 0;
  	}
  
  	do {
  		rc = os_write_file(info->kick_fd, &n, sizeof(n));
  	} while (rc == -EINTR);
  	return !WARN(rc != sizeof(n), "write returned %d\n", rc);
  }
  
  static irqreturn_t vu_interrupt(int irq, void *opaque)
  {
  	struct virtqueue *vq = opaque;
  	struct virtio_uml_vq_info *info = vq->priv;
  	uint64_t n;
  	int rc;
  	irqreturn_t ret = IRQ_NONE;
  
  	do {
  		rc = os_read_file(info->call_fd, &n, sizeof(n));
  		if (rc == sizeof(n))
  			ret |= vring_interrupt(irq, vq);
  	} while (rc == sizeof(n) || rc == -EINTR);
  	WARN(rc != -EAGAIN, "read returned %d\n", rc);
  	return ret;
  }
  
  
  static void vu_get(struct virtio_device *vdev, unsigned offset,
  		   void *buf, unsigned len)
  {
  	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
  
  	vhost_user_get_config(vu_dev, offset, buf, len);
  }
  
  static void vu_set(struct virtio_device *vdev, unsigned offset,
  		   const void *buf, unsigned len)
  {
  	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
  
  	vhost_user_set_config(vu_dev, offset, buf, len);
  }
  
  static u8 vu_get_status(struct virtio_device *vdev)
  {
  	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
  
  	return vu_dev->status;
  }
  
  static void vu_set_status(struct virtio_device *vdev, u8 status)
  {
  	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
  
  	vu_dev->status = status;
  }
  
  static void vu_reset(struct virtio_device *vdev)
  {
  	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
  
  	vu_dev->status = 0;
  }
  
  static void vu_del_vq(struct virtqueue *vq)
  {
  	struct virtio_uml_vq_info *info = vq->priv;
  
  	if (info->call_fd >= 0) {
  		um_free_irq(VIRTIO_IRQ, vq);
  		os_close_file(info->call_fd);
  	}
  
  	if (info->kick_fd >= 0)
  		os_close_file(info->kick_fd);
  
  	vring_del_virtqueue(vq);
  	kfree(info);
  }
  
  static void vu_del_vqs(struct virtio_device *vdev)
  {
  	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
  	struct virtqueue *vq, *n;
  	u64 features;
  
  	/* Note: reverse order as a workaround to a decoding bug in snabb */
  	list_for_each_entry_reverse(vq, &vdev->vqs, list)
  		WARN_ON(vhost_user_set_vring_enable(vu_dev, vq->index, false));
  
  	/* Ensure previous messages have been processed */
  	WARN_ON(vhost_user_get_features(vu_dev, &features));
  
  	list_for_each_entry_safe(vq, n, &vdev->vqs, list)
  		vu_del_vq(vq);
  }
  
  static int vu_setup_vq_call_fd(struct virtio_uml_device *vu_dev,
  			       struct virtqueue *vq)
  {
  	struct virtio_uml_vq_info *info = vq->priv;
  	int call_fds[2];
  	int rc;
  
  	/* no call FD needed/desired in this case */
  	if (vu_dev->protocol_features &
  			BIT_ULL(VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS) &&
  	    vu_dev->protocol_features &
  			BIT_ULL(VHOST_USER_PROTOCOL_F_SLAVE_REQ)) {
  		info->call_fd = -1;
  		return 0;
  	}
  
  	/* Use a pipe for call fd, since SIGIO is not supported for eventfd */
  	rc = os_pipe(call_fds, true, true);
  	if (rc < 0)
  		return rc;
  
  	info->call_fd = call_fds[0];
  	rc = um_request_irq(VIRTIO_IRQ, info->call_fd, IRQ_READ,
  			    vu_interrupt, IRQF_SHARED, info->name, vq);
  	if (rc)
  		goto close_both;
  
  	rc = vhost_user_set_vring_call(vu_dev, vq->index, call_fds[1]);
  	if (rc)
  		goto release_irq;
  
  	goto out;
  
  release_irq:
  	um_free_irq(VIRTIO_IRQ, vq);
  close_both:
  	os_close_file(call_fds[0]);
  out:
  	/* Close (unused) write end of call fds */
  	os_close_file(call_fds[1]);
  
  	return rc;
  }
  
  #ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
  static void vu_defer_irq_handle(struct time_travel_event *d)
  {
  	struct virtio_uml_vq_info *info;
  
  	info = container_of(d, struct virtio_uml_vq_info, defer);
  	info->callback(info->vq);
  }
  
  static void vu_defer_irq_callback(struct virtqueue *vq)
  {
  	struct virtio_uml_vq_info *info = vq->priv;
  
  	time_travel_add_irq_event(&info->defer);
  }
  #endif
  
  static struct virtqueue *vu_setup_vq(struct virtio_device *vdev,
  				     unsigned index, vq_callback_t *callback,
  				     const char *name, bool ctx)
  {
  	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
  	struct platform_device *pdev = vu_dev->pdev;
  	struct virtio_uml_vq_info *info;
  	struct virtqueue *vq;
  	int num = MAX_SUPPORTED_QUEUE_SIZE;
  	int rc;
  
  	info = kzalloc(sizeof(*info), GFP_KERNEL);
  	if (!info) {
  		rc = -ENOMEM;
  		goto error_kzalloc;
  	}
  	snprintf(info->name, sizeof(info->name), "%s.%d-%s", pdev->name,
  		 pdev->id, name);
  
  #ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
  	/*
  	 * When we get an interrupt, we must bounce it through the simulation
  	 * calendar (the simtime device), except for the simtime device itself
  	 * since that's part of the simulation control.
  	 */
  	if (time_travel_mode == TT_MODE_EXTERNAL && callback) {
  		info->callback = callback;
  		callback = vu_defer_irq_callback;
  		time_travel_set_event_fn(&info->defer, vu_defer_irq_handle);
  	}
  #endif
  
  	vq = vring_create_virtqueue(index, num, PAGE_SIZE, vdev, true, true,
  				    ctx, vu_notify, callback, info->name);
  	if (!vq) {
  		rc = -ENOMEM;
  		goto error_create;
  	}
  	vq->priv = info;
  	num = virtqueue_get_vring_size(vq);
  #ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
  	info->vq = vq;
  #endif
  
  	if (vu_dev->protocol_features &
  			BIT_ULL(VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS)) {
  		info->kick_fd = -1;
  	} else {
  		rc = os_eventfd(0, 0);
  		if (rc < 0)
  			goto error_kick;
  		info->kick_fd = rc;
  	}
  
  	rc = vu_setup_vq_call_fd(vu_dev, vq);
  	if (rc)
  		goto error_call;
  
  	rc = vhost_user_set_vring_num(vu_dev, index, num);
  	if (rc)
  		goto error_setup;
  
  	rc = vhost_user_set_vring_base(vu_dev, index, 0);
  	if (rc)
  		goto error_setup;
  
  	rc = vhost_user_set_vring_addr(vu_dev, index,
  				       virtqueue_get_desc_addr(vq),
  				       virtqueue_get_used_addr(vq),
  				       virtqueue_get_avail_addr(vq),
  				       (u64) -1);
  	if (rc)
  		goto error_setup;
  
  	return vq;
  
  error_setup:
  	if (info->call_fd >= 0) {
  		um_free_irq(VIRTIO_IRQ, vq);
  		os_close_file(info->call_fd);
  	}
  error_call:
  	if (info->kick_fd >= 0)
  		os_close_file(info->kick_fd);
  error_kick:
  	vring_del_virtqueue(vq);
  error_create:
  	kfree(info);
  error_kzalloc:
  	return ERR_PTR(rc);
  }
  
  static int vu_find_vqs(struct virtio_device *vdev, unsigned nvqs,
  		       struct virtqueue *vqs[], vq_callback_t *callbacks[],
  		       const char * const names[], const bool *ctx,
  		       struct irq_affinity *desc)
  {
  	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
  	int i, queue_idx = 0, rc;
  	struct virtqueue *vq;
  
  	rc = vhost_user_set_mem_table(vu_dev);
  	if (rc)
  		return rc;
  
  	for (i = 0; i < nvqs; ++i) {
  		if (!names[i]) {
  			vqs[i] = NULL;
  			continue;
  		}
  
  		vqs[i] = vu_setup_vq(vdev, queue_idx++, callbacks[i], names[i],
  				     ctx ? ctx[i] : false);
  		if (IS_ERR(vqs[i])) {
  			rc = PTR_ERR(vqs[i]);
  			goto error_setup;
  		}
  	}
  
  	list_for_each_entry(vq, &vdev->vqs, list) {
  		struct virtio_uml_vq_info *info = vq->priv;
  
  		if (info->kick_fd >= 0) {
  			rc = vhost_user_set_vring_kick(vu_dev, vq->index,
  						       info->kick_fd);
  			if (rc)
  				goto error_setup;
  		}
  
  		rc = vhost_user_set_vring_enable(vu_dev, vq->index, true);
  		if (rc)
  			goto error_setup;
  	}
  
  	return 0;
  
  error_setup:
  	vu_del_vqs(vdev);
  	return rc;
  }
  
  static u64 vu_get_features(struct virtio_device *vdev)
  {
  	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
  
  	return vu_dev->features;
  }
  
  static int vu_finalize_features(struct virtio_device *vdev)
  {
  	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
  	u64 supported = vdev->features & VHOST_USER_SUPPORTED_F;
  
  	vring_transport_features(vdev);
  	vu_dev->features = vdev->features | supported;
  
  	return vhost_user_set_features(vu_dev, vu_dev->features);
  }
  
  static const char *vu_bus_name(struct virtio_device *vdev)
  {
  	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
  
  	return vu_dev->pdev->name;
  }
  
  static const struct virtio_config_ops virtio_uml_config_ops = {
  	.get = vu_get,
  	.set = vu_set,
  	.get_status = vu_get_status,
  	.set_status = vu_set_status,
  	.reset = vu_reset,
  	.find_vqs = vu_find_vqs,
  	.del_vqs = vu_del_vqs,
  	.get_features = vu_get_features,
  	.finalize_features = vu_finalize_features,
  	.bus_name = vu_bus_name,
  };
  
  static void virtio_uml_release_dev(struct device *d)
  {
  	struct virtio_device *vdev =
  			container_of(d, struct virtio_device, dev);
  	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
  
  	/* might not have been opened due to not negotiating the feature */
  	if (vu_dev->req_fd >= 0) {
  		um_free_irq(VIRTIO_IRQ, vu_dev);
  		os_close_file(vu_dev->req_fd);
  	}
  
  	os_close_file(vu_dev->sock);
  }
  
  /* Platform device */
  
  static int virtio_uml_probe(struct platform_device *pdev)
  {
  	struct virtio_uml_platform_data *pdata = pdev->dev.platform_data;
  	struct virtio_uml_device *vu_dev;
  	int rc;
  
  	if (!pdata)
  		return -EINVAL;
  
  	vu_dev = devm_kzalloc(&pdev->dev, sizeof(*vu_dev), GFP_KERNEL);
  	if (!vu_dev)
  		return -ENOMEM;
  
  	vu_dev->vdev.dev.parent = &pdev->dev;
  	vu_dev->vdev.dev.release = virtio_uml_release_dev;
  	vu_dev->vdev.config = &virtio_uml_config_ops;
  	vu_dev->vdev.id.device = pdata->virtio_device_id;
  	vu_dev->vdev.id.vendor = VIRTIO_DEV_ANY_ID;
  	vu_dev->pdev = pdev;
  	vu_dev->req_fd = -1;
  
  	do {
  		rc = os_connect_socket(pdata->socket_path);
  	} while (rc == -EINTR);
  	if (rc < 0)
  		return rc;
  	vu_dev->sock = rc;
  
  	spin_lock_init(&vu_dev->sock_lock);
  
  	rc = vhost_user_init(vu_dev);
  	if (rc)
  		goto error_init;
  
  	platform_set_drvdata(pdev, vu_dev);
  
  	rc = register_virtio_device(&vu_dev->vdev);
  	if (rc)
  		put_device(&vu_dev->vdev.dev);
  	vu_dev->registered = 1;
  	return rc;
  
  error_init:
  	os_close_file(vu_dev->sock);
  	return rc;
  }
  
  static int virtio_uml_remove(struct platform_device *pdev)
  {
  	struct virtio_uml_device *vu_dev = platform_get_drvdata(pdev);
  
  	unregister_virtio_device(&vu_dev->vdev);
  	return 0;
  }
  
  /* Command line device list */
  
  static void vu_cmdline_release_dev(struct device *d)
  {
  }
  
  static struct device vu_cmdline_parent = {
  	.init_name = "virtio-uml-cmdline",
  	.release = vu_cmdline_release_dev,
  };
  
  static bool vu_cmdline_parent_registered;
  static int vu_cmdline_id;
  
  static int vu_unregister_cmdline_device(struct device *dev, void *data)
  {
  	struct platform_device *pdev = to_platform_device(dev);
  	struct virtio_uml_platform_data *pdata = pdev->dev.platform_data;
  
  	kfree(pdata->socket_path);
  	platform_device_unregister(pdev);
  	return 0;
  }
  
  static void vu_conn_broken(struct work_struct *wk)
  {
  	struct virtio_uml_platform_data *pdata;
  
  	pdata = container_of(wk, struct virtio_uml_platform_data, conn_broken_wk);
  	vu_unregister_cmdline_device(&pdata->pdev->dev, NULL);
  }
  
  static int vu_cmdline_set(const char *device, const struct kernel_param *kp)
  {
  	const char *ids = strchr(device, ':');
  	unsigned int virtio_device_id;
  	int processed, consumed, err;
  	char *socket_path;
  	struct virtio_uml_platform_data pdata, *ppdata;
  	struct platform_device *pdev;
  
  	if (!ids || ids == device)
  		return -EINVAL;
  
  	processed = sscanf(ids, ":%u%n:%d%n",
  			   &virtio_device_id, &consumed,
  			   &vu_cmdline_id, &consumed);
  
  	if (processed < 1 || ids[consumed])
  		return -EINVAL;
  
  	if (!vu_cmdline_parent_registered) {
  		err = device_register(&vu_cmdline_parent);
  		if (err) {
  			pr_err("Failed to register parent device!\n");
  			put_device(&vu_cmdline_parent);
  			return err;
  		}
  		vu_cmdline_parent_registered = true;
  	}
  
  	socket_path = kmemdup_nul(device, ids - device, GFP_KERNEL);
  	if (!socket_path)
  		return -ENOMEM;
  
  	pdata.virtio_device_id = (u32) virtio_device_id;
  	pdata.socket_path = socket_path;
  
  	pr_info("Registering device virtio-uml.%d id=%d at %s\n",
  		vu_cmdline_id, virtio_device_id, socket_path);
  
  	pdev = platform_device_register_data(&vu_cmdline_parent, "virtio-uml",
  					     vu_cmdline_id++, &pdata,
  					     sizeof(pdata));
  	err = PTR_ERR_OR_ZERO(pdev);
  	if (err)
  		goto free;
  
  	ppdata = pdev->dev.platform_data;
  	ppdata->pdev = pdev;
  	INIT_WORK(&ppdata->conn_broken_wk, vu_conn_broken);
  
  	return 0;
  
  free:
  	kfree(socket_path);
  	return err;
  }
  
  static int vu_cmdline_get_device(struct device *dev, void *data)
  {
  	struct platform_device *pdev = to_platform_device(dev);
  	struct virtio_uml_platform_data *pdata = pdev->dev.platform_data;
  	char *buffer = data;
  	unsigned int len = strlen(buffer);
  
  	snprintf(buffer + len, PAGE_SIZE - len, "%s:%d:%d\n",
  		 pdata->socket_path, pdata->virtio_device_id, pdev->id);
  	return 0;
  }
  
  static int vu_cmdline_get(char *buffer, const struct kernel_param *kp)
  {
  	buffer[0] = '\0';
  	if (vu_cmdline_parent_registered)
  		device_for_each_child(&vu_cmdline_parent, buffer,
  				      vu_cmdline_get_device);
  	return strlen(buffer) + 1;
  }
  
  static const struct kernel_param_ops vu_cmdline_param_ops = {
  	.set = vu_cmdline_set,
  	.get = vu_cmdline_get,
  };
  
  device_param_cb(device, &vu_cmdline_param_ops, NULL, S_IRUSR);
  __uml_help(vu_cmdline_param_ops,
  "virtio_uml.device=<socket>:<virtio_id>[:<platform_id>]\n"
  "    Configure a virtio device over a vhost-user socket.\n"
  "    See virtio_ids.h for a list of possible virtio device id values.\n"
  "    Optionally use a specific platform_device id.\n\n"
  );
  
  
  static void vu_unregister_cmdline_devices(void)
  {
  	if (vu_cmdline_parent_registered) {
  		device_for_each_child(&vu_cmdline_parent, NULL,
  				      vu_unregister_cmdline_device);
  		device_unregister(&vu_cmdline_parent);
  		vu_cmdline_parent_registered = false;
  	}
  }
  
  /* Platform driver */
  
  static const struct of_device_id virtio_uml_match[] = {
  	{ .compatible = "virtio,uml", },
  	{ }
  };
  MODULE_DEVICE_TABLE(of, virtio_uml_match);
  
  static struct platform_driver virtio_uml_driver = {
  	.probe = virtio_uml_probe,
  	.remove = virtio_uml_remove,
  	.driver = {
  		.name = "virtio-uml",
  		.of_match_table = virtio_uml_match,
  	},
  };
  
  static int __init virtio_uml_init(void)
  {
  	return platform_driver_register(&virtio_uml_driver);
  }
  
  static void __exit virtio_uml_exit(void)
  {
  	platform_driver_unregister(&virtio_uml_driver);
  	vu_unregister_cmdline_devices();
  }
  
  module_init(virtio_uml_init);
  module_exit(virtio_uml_exit);
  __uml_exitcall(virtio_uml_exit);
  
  MODULE_DESCRIPTION("UML driver for vhost-user virtio devices");
  MODULE_LICENSE("GPL");
  