// 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 <linux/virtio-uml.h>
#include <shared/as-layout.h>
#include <irq_kern.h>
#include <init.h>
#include <os.h>
#include "vhost_user.h"

#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, irq;
        u64 features;
        u64 protocol_features;
        u8 status;
        u8 registered:1;
        u8 suspended:1;
        u8 no_vq_suspend:1;

        u8 config_changed_irq:1;
        uint64_t vq_irq_vq_map;
};

struct virtio_uml_vq_info {
        int kick_fd, call_fd;
        char name[32];
        bool suspended;
};

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;

        if (!len)
                return 0;

        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_read_message(struct virtio_uml_device *vu_dev,
                                       struct time_travel_event *ev)
{
        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:
                vu_dev->config_changed_irq = true;
                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;
                                vu_dev->vq_irq_vq_map |= BIT_ULL(vq->index);
                                break;
                        }
                }
                break;
        case VHOST_USER_SLAVE_IOTLB_MSG:
                /* not supported - VIRTIO_F_ACCESS_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 (ev && !vu_dev->suspended)
                time_travel_add_irq_event(ev);

        if (msg.msg.header.flags & VHOST_USER_FLAG_NEED_REPLY)
                vhost_user_reply(vu_dev, &msg.msg, response);

        return IRQ_HANDLED;
}

static irqreturn_t vu_req_interrupt(int irq, void *data)
{
        struct virtio_uml_device *vu_dev = data;
        irqreturn_t ret = IRQ_HANDLED;

        if (!um_irq_timetravel_handler_used())
                ret = vu_req_read_message(vu_dev, NULL);

        if (vu_dev->vq_irq_vq_map) {
                struct virtqueue *vq;

                virtio_device_for_each_vq((&vu_dev->vdev), vq) {
                        if (vu_dev->vq_irq_vq_map & BIT_ULL(vq->index))
                                vring_interrupt(0 /* ignored */, vq);
                }
                vu_dev->vq_irq_vq_map = 0;
        } else if (vu_dev->config_changed_irq) {
                virtio_config_changed(&vu_dev->vdev);
                vu_dev->config_changed_irq = false;
        }

        return ret;
}

static void vu_req_interrupt_comm_handler(int irq, int fd, void *data,
                                          struct time_travel_event *ev)
{
        vu_req_read_message(data, ev);
}

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_tt(UM_IRQ_ALLOC, vu_dev->req_fd, IRQ_READ,
                               vu_req_interrupt, IRQF_SHARED,
                               vu_dev->pdev->name, vu_dev,
                               vu_req_interrupt_comm_handler);
        if (rc < 0)
                goto err_close;

        vu_dev->irq = rc;

        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(vu_dev->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;

        if (info->suspended)
                return true;

        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) {
                struct virtio_uml_device *vu_dev;

                vu_dev = to_virtio_uml_device(vq->vdev);

                um_free_irq(vu_dev->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(vu_dev->irq, info->call_fd, IRQ_READ,
                            vu_interrupt, IRQF_SHARED, info->name, vq);
        if (rc < 0)
                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(vu_dev->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;
}

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);

        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);

        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(vu_dev->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;

        /* not supported for now */
        if (WARN_ON(nvqs > 64))
                return -EINVAL;

        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(vu_dev->irq, vu_dev);
                os_close_file(vu_dev->req_fd);
        }

        os_close_file(vu_dev->sock);
        kfree(vu_dev);
}

void virtio_uml_set_no_vq_suspend(struct virtio_device *vdev,
                                  bool no_vq_suspend)
{
        struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);

        if (WARN_ON(vdev->config != &virtio_uml_config_ops))
                return;

        vu_dev->no_vq_suspend = no_vq_suspend;
        dev_info(&vdev->dev, "%sabled VQ suspend\n",
                 no_vq_suspend ? "dis" : "en");
}

/* 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 = kzalloc(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)
                goto error_free;
        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);

        device_set_wakeup_capable(&vu_dev->vdev.dev, true);

        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);
error_free:
        kfree(vu_dev);
        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 int virtio_uml_suspend(struct platform_device *pdev, pm_message_t state)
{
        struct virtio_uml_device *vu_dev = platform_get_drvdata(pdev);

        if (!vu_dev->no_vq_suspend) {
                struct virtqueue *vq;

                virtio_device_for_each_vq((&vu_dev->vdev), vq) {
                        struct virtio_uml_vq_info *info = vq->priv;

                        info->suspended = true;
                        vhost_user_set_vring_enable(vu_dev, vq->index, false);
                }
        }

        if (!device_may_wakeup(&vu_dev->vdev.dev)) {
                vu_dev->suspended = true;
                return 0;
        }

        return irq_set_irq_wake(vu_dev->irq, 1);
}

static int virtio_uml_resume(struct platform_device *pdev)
{
        struct virtio_uml_device *vu_dev = platform_get_drvdata(pdev);

        if (!vu_dev->no_vq_suspend) {
                struct virtqueue *vq;

                virtio_device_for_each_vq((&vu_dev->vdev), vq) {
                        struct virtio_uml_vq_info *info = vq->priv;

                        info->suspended = false;
                        vhost_user_set_vring_enable(vu_dev, vq->index, true);
                }
        }

        vu_dev->suspended = false;

        if (!device_may_wakeup(&vu_dev->vdev.dev))
                return 0;

        return irq_set_irq_wake(vu_dev->irq, 0);
}

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,
        },
        .suspend = virtio_uml_suspend,
        .resume = virtio_uml_resume,
};

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");