virtio_scsi.c

Go to the documentation of this file.

/*
 * Virtio SCSI HBA driver
 *
 * Copyright IBM Corp. 2010
 * Copyright Red Hat, Inc. 2011
 *
 * Authors:
 *  Stefan Hajnoczi   <[email protected]>
 *  Paolo Bonzini   <[email protected]>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 *
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/mempool.h>
#include <linux/virtio.h>
#include <linux/virtio_ids.h>
#include <linux/virtio_config.h>
#include <linux/virtio_scsi.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_cmnd.h>

#define VIRTIO_SCSI_MEMPOOL_SZ 64
#define VIRTIO_SCSI_EVENT_LEN 8

/* Command queue element */
struct virtio_scsi_cmd {
    struct scsi_cmnd *sc;
    struct completion *comp;
    union {
        struct virtio_scsi_cmd_req       cmd;
        struct virtio_scsi_ctrl_tmf_req  tmf;
        struct virtio_scsi_ctrl_an_req   an;
    } req;
    union {
        struct virtio_scsi_cmd_resp      cmd;
        struct virtio_scsi_ctrl_tmf_resp tmf;
        struct virtio_scsi_ctrl_an_resp  an;
        struct virtio_scsi_event         evt;
    } resp;
} ____cacheline_aligned_in_smp;

struct virtio_scsi_event_node {
    struct virtio_scsi *vscsi;
    struct virtio_scsi_event event;
    struct work_struct work;
};

struct virtio_scsi_vq {
    /* Protects vq */
    spinlock_t vq_lock;

    struct virtqueue *vq;
};

/* Per-target queue state */
struct virtio_scsi_target_state {
    /* Protects sg.  Lock hierarchy is tgt_lock -> vq_lock.  */
    spinlock_t tgt_lock;

    /* For sglist construction when adding commands to the virtqueue.  */
    struct scatterlist sg[];
};

/* Driver instance state */
struct virtio_scsi {
    struct virtio_device *vdev;

    struct virtio_scsi_vq ctrl_vq;
    struct virtio_scsi_vq event_vq;
    struct virtio_scsi_vq req_vq;

    /* Get some buffers ready for event vq */
    struct virtio_scsi_event_node event_list[VIRTIO_SCSI_EVENT_LEN];

    struct virtio_scsi_target_state *tgt[];
};

static struct kmem_cache *virtscsi_cmd_cache;
static mempool_t *virtscsi_cmd_pool;

static inline struct Scsi_Host *virtio_scsi_host(struct virtio_device *vdev)
{
    return vdev->priv;
}

static void virtscsi_compute_resid(struct scsi_cmnd *sc, u32 resid)
{
    if (!resid)
        return;

    if (!scsi_bidi_cmnd(sc)) {
        scsi_set_resid(sc, resid);
        return;
    }

    scsi_in(sc)->resid = min(resid, scsi_in(sc)->length);
    scsi_out(sc)->resid = resid - scsi_in(sc)->resid;
}

static void virtscsi_complete_cmd(void *buf)
{
    struct virtio_scsi_cmd *cmd = buf;
    struct scsi_cmnd *sc = cmd->sc;
    struct virtio_scsi_cmd_resp *resp = &cmd->resp.cmd;

    dev_dbg(&sc->device->sdev_gendev,
        "cmd %p response %u status %#02x sense_len %u\n",
        sc, resp->response, resp->status, resp->sense_len);

    sc->result = resp->status;
    virtscsi_compute_resid(sc, resp->resid);
    switch (resp->response) {
    case VIRTIO_SCSI_S_OK:
        set_host_byte(sc, DID_OK);
        break;
    case VIRTIO_SCSI_S_OVERRUN:
        set_host_byte(sc, DID_ERROR);
        break;
    case VIRTIO_SCSI_S_ABORTED:
        set_host_byte(sc, DID_ABORT);
        break;
    case VIRTIO_SCSI_S_BAD_TARGET:
        set_host_byte(sc, DID_BAD_TARGET);
        break;
    case VIRTIO_SCSI_S_RESET:
        set_host_byte(sc, DID_RESET);
        break;
    case VIRTIO_SCSI_S_BUSY:
        set_host_byte(sc, DID_BUS_BUSY);
        break;
    case VIRTIO_SCSI_S_TRANSPORT_FAILURE:
        set_host_byte(sc, DID_TRANSPORT_DISRUPTED);
        break;
    case VIRTIO_SCSI_S_TARGET_FAILURE:
        set_host_byte(sc, DID_TARGET_FAILURE);
        break;
    case VIRTIO_SCSI_S_NEXUS_FAILURE:
        set_host_byte(sc, DID_NEXUS_FAILURE);
        break;
    default:
        scmd_printk(KERN_WARNING, sc, "Unknown response %d",
                resp->response);
        /* fall through */
    case VIRTIO_SCSI_S_FAILURE:
        set_host_byte(sc, DID_ERROR);
        break;
    }

    WARN_ON(resp->sense_len > VIRTIO_SCSI_SENSE_SIZE);
    if (sc->sense_buffer) {
        memcpy(sc->sense_buffer, resp->sense,
               min_t(u32, resp->sense_len, VIRTIO_SCSI_SENSE_SIZE));
        if (resp->sense_len)
            set_driver_byte(sc, DRIVER_SENSE);
    }

    mempool_free(cmd, virtscsi_cmd_pool);
    sc->scsi_done(sc);
}

static void virtscsi_vq_done(struct virtqueue *vq, void (*fn)(void *buf))
{
    void *buf;
    unsigned int len;

    do {
        virtqueue_disable_cb(vq);
        while ((buf = virtqueue_get_buf(vq, &len)) != NULL)
            fn(buf);
    } while (!virtqueue_enable_cb(vq));
}

static void virtscsi_req_done(struct virtqueue *vq)
{
    struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
    struct virtio_scsi *vscsi = shost_priv(sh);
    unsigned long flags;

    spin_lock_irqsave(&vscsi->req_vq.vq_lock, flags);
    virtscsi_vq_done(vq, virtscsi_complete_cmd);
    spin_unlock_irqrestore(&vscsi->req_vq.vq_lock, flags);
};

static void virtscsi_complete_free(void *buf)
{
    struct virtio_scsi_cmd *cmd = buf;

    if (cmd->comp)
        complete_all(cmd->comp);
    else
        mempool_free(cmd, virtscsi_cmd_pool);
}

static void virtscsi_ctrl_done(struct virtqueue *vq)
{
    struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
    struct virtio_scsi *vscsi = shost_priv(sh);
    unsigned long flags;

    spin_lock_irqsave(&vscsi->ctrl_vq.vq_lock, flags);
    virtscsi_vq_done(vq, virtscsi_complete_free);
    spin_unlock_irqrestore(&vscsi->ctrl_vq.vq_lock, flags);
};

static int virtscsi_kick_event(struct virtio_scsi *vscsi,
                   struct virtio_scsi_event_node *event_node)
{
    int ret;
    struct scatterlist sg;
    unsigned long flags;

    sg_init_one(&sg, &event_node->event, sizeof(struct virtio_scsi_event));

    spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);

    ret = virtqueue_add_buf(vscsi->event_vq.vq, &sg, 0, 1, event_node, GFP_ATOMIC);
    if (ret >= 0)
        virtqueue_kick(vscsi->event_vq.vq);

    spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags);

    return ret;
}

static int virtscsi_kick_event_all(struct virtio_scsi *vscsi)
{
    int i;

    for (i = 0; i < VIRTIO_SCSI_EVENT_LEN; i++) {
        vscsi->event_list[i].vscsi = vscsi;
        virtscsi_kick_event(vscsi, &vscsi->event_list[i]);
    }

    return 0;
}

static void virtscsi_cancel_event_work(struct virtio_scsi *vscsi)
{
    int i;

    for (i = 0; i < VIRTIO_SCSI_EVENT_LEN; i++)
        cancel_work_sync(&vscsi->event_list[i].work);
}

static void virtscsi_handle_transport_reset(struct virtio_scsi *vscsi,
                        struct virtio_scsi_event *event)
{
    struct scsi_device *sdev;
    struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
    unsigned int target = event->lun[1];
    unsigned int lun = (event->lun[2] << 8) | event->lun[3];

    switch (event->reason) {
    case VIRTIO_SCSI_EVT_RESET_RESCAN:
        scsi_add_device(shost, 0, target, lun);
        break;
    case VIRTIO_SCSI_EVT_RESET_REMOVED:
        sdev = scsi_device_lookup(shost, 0, target, lun);
        if (sdev) {
            scsi_remove_device(sdev);
            scsi_device_put(sdev);
        } else {
            pr_err("SCSI device %d 0 %d %d not found\n",
                shost->host_no, target, lun);
        }
        break;
    default:
        pr_info("Unsupport virtio scsi event reason %x\n", event->reason);
    }
}

static void virtscsi_handle_param_change(struct virtio_scsi *vscsi,
                     struct virtio_scsi_event *event)
{
    struct scsi_device *sdev;
    struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
    unsigned int target = event->lun[1];
    unsigned int lun = (event->lun[2] << 8) | event->lun[3];
    u8 asc = event->reason & 255;
    u8 ascq = event->reason >> 8;

    sdev = scsi_device_lookup(shost, 0, target, lun);
    if (!sdev) {
        pr_err("SCSI device %d 0 %d %d not found\n",
            shost->host_no, target, lun);
        return;
    }

    /* Handle "Parameters changed", "Mode parameters changed", and
       "Capacity data has changed".  */
    if (asc == 0x2a && (ascq == 0x00 || ascq == 0x01 || ascq == 0x09))
        scsi_rescan_device(&sdev->sdev_gendev);

    scsi_device_put(sdev);
}

static void virtscsi_handle_event(struct work_struct *work)
{
    struct virtio_scsi_event_node *event_node =
        container_of(work, struct virtio_scsi_event_node, work);
    struct virtio_scsi *vscsi = event_node->vscsi;
    struct virtio_scsi_event *event = &event_node->event;

    if (event->event & VIRTIO_SCSI_T_EVENTS_MISSED) {
        event->event &= ~VIRTIO_SCSI_T_EVENTS_MISSED;
        scsi_scan_host(virtio_scsi_host(vscsi->vdev));
    }

    switch (event->event) {
    case VIRTIO_SCSI_T_NO_EVENT:
        break;
    case VIRTIO_SCSI_T_TRANSPORT_RESET:
        virtscsi_handle_transport_reset(vscsi, event);
        break;
    case VIRTIO_SCSI_T_PARAM_CHANGE:
        virtscsi_handle_param_change(vscsi, event);
        break;
    default:
        pr_err("Unsupport virtio scsi event %x\n", event->event);
    }
    virtscsi_kick_event(vscsi, event_node);
}

static void virtscsi_complete_event(void *buf)
{
    struct virtio_scsi_event_node *event_node = buf;

    INIT_WORK(&event_node->work, virtscsi_handle_event);
    schedule_work(&event_node->work);
}

static void virtscsi_event_done(struct virtqueue *vq)
{
    struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
    struct virtio_scsi *vscsi = shost_priv(sh);
    unsigned long flags;

    spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);
    virtscsi_vq_done(vq, virtscsi_complete_event);
    spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags);
};

static void virtscsi_map_sgl(struct scatterlist *sg, unsigned int *p_idx,
                 struct scsi_data_buffer *sdb)
{
    struct sg_table *table = &sdb->table;
    struct scatterlist *sg_elem;
    unsigned int idx = *p_idx;
    int i;

    for_each_sg(table->sgl, sg_elem, table->nents, i)
        sg[idx++] = *sg_elem;

    *p_idx = idx;
}

static void virtscsi_map_cmd(struct virtio_scsi_target_state *tgt,
                 struct virtio_scsi_cmd *cmd,
                 unsigned *out_num, unsigned *in_num,
                 size_t req_size, size_t resp_size)
{
    struct scsi_cmnd *sc = cmd->sc;
    struct scatterlist *sg = tgt->sg;
    unsigned int idx = 0;

    /* Request header.  */
    sg_set_buf(&sg[idx++], &cmd->req, req_size);

    /* Data-out buffer.  */
    if (sc && sc->sc_data_direction != DMA_FROM_DEVICE)
        virtscsi_map_sgl(sg, &idx, scsi_out(sc));

    *out_num = idx;

    /* Response header.  */
    sg_set_buf(&sg[idx++], &cmd->resp, resp_size);

    /* Data-in buffer */
    if (sc && sc->sc_data_direction != DMA_TO_DEVICE)
        virtscsi_map_sgl(sg, &idx, scsi_in(sc));

    *in_num = idx - *out_num;
}

static int virtscsi_kick_cmd(struct virtio_scsi_target_state *tgt,
                 struct virtio_scsi_vq *vq,
                 struct virtio_scsi_cmd *cmd,
                 size_t req_size, size_t resp_size, gfp_t gfp)
{
    unsigned int out_num, in_num;
    unsigned long flags;
    int ret;

    spin_lock_irqsave(&tgt->tgt_lock, flags);
    virtscsi_map_cmd(tgt, cmd, &out_num, &in_num, req_size, resp_size);

    spin_lock(&vq->vq_lock);
    ret = virtqueue_add_buf(vq->vq, tgt->sg, out_num, in_num, cmd, gfp);
    spin_unlock(&tgt->tgt_lock);
    if (ret >= 0)
        ret = virtqueue_kick_prepare(vq->vq);

    spin_unlock_irqrestore(&vq->vq_lock, flags);

    if (ret > 0)
        virtqueue_notify(vq->vq);
    return ret;
}

static int virtscsi_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *sc)
{
    struct virtio_scsi *vscsi = shost_priv(sh);
    struct virtio_scsi_target_state *tgt = vscsi->tgt[sc->device->id];
    struct virtio_scsi_cmd *cmd;
    int ret;

    struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
    BUG_ON(scsi_sg_count(sc) > shost->sg_tablesize);

    /* TODO: check feature bit and fail if unsupported?  */
    BUG_ON(sc->sc_data_direction == DMA_BIDIRECTIONAL);

    dev_dbg(&sc->device->sdev_gendev,
        "cmd %p CDB: %#02x\n", sc, sc->cmnd[0]);

    ret = SCSI_MLQUEUE_HOST_BUSY;
    cmd = mempool_alloc(virtscsi_cmd_pool, GFP_ATOMIC);
    if (!cmd)
        goto out;

    memset(cmd, 0, sizeof(*cmd));
    cmd->sc = sc;
    cmd->req.cmd = (struct virtio_scsi_cmd_req){
        .lun[0] = 1,
        .lun[1] = sc->device->id,
        .lun[2] = (sc->device->lun >> 8) | 0x40,
        .lun[3] = sc->device->lun & 0xff,
        .tag = (unsigned long)sc,
        .task_attr = VIRTIO_SCSI_S_SIMPLE,
        .prio = 0,
        .crn = 0,
    };

    BUG_ON(sc->cmd_len > VIRTIO_SCSI_CDB_SIZE);
    memcpy(cmd->req.cmd.cdb, sc->cmnd, sc->cmd_len);

    if (virtscsi_kick_cmd(tgt, &vscsi->req_vq, cmd,
                  sizeof cmd->req.cmd, sizeof cmd->resp.cmd,
                  GFP_ATOMIC) >= 0)
        ret = 0;

out:
    return ret;
}

static int virtscsi_tmf(struct virtio_scsi *vscsi, struct virtio_scsi_cmd *cmd)
{
    DECLARE_COMPLETION_ONSTACK(comp);
    struct virtio_scsi_target_state *tgt = vscsi->tgt[cmd->sc->device->id];
    int ret = FAILED;

    cmd->comp = &comp;
    if (virtscsi_kick_cmd(tgt, &vscsi->ctrl_vq, cmd,
                  sizeof cmd->req.tmf, sizeof cmd->resp.tmf,
                  GFP_NOIO) < 0)
        goto out;

    wait_for_completion(&comp);
    if (cmd->resp.tmf.response == VIRTIO_SCSI_S_OK ||
        cmd->resp.tmf.response == VIRTIO_SCSI_S_FUNCTION_SUCCEEDED)
        ret = SUCCESS;

out:
    mempool_free(cmd, virtscsi_cmd_pool);
    return ret;
}

static int virtscsi_device_reset(struct scsi_cmnd *sc)
{
    struct virtio_scsi *vscsi = shost_priv(sc->device->host);
    struct virtio_scsi_cmd *cmd;

    sdev_printk(KERN_INFO, sc->device, "device reset\n");
    cmd = mempool_alloc(virtscsi_cmd_pool, GFP_NOIO);
    if (!cmd)
        return FAILED;

    memset(cmd, 0, sizeof(*cmd));
    cmd->sc = sc;
    cmd->req.tmf = (struct virtio_scsi_ctrl_tmf_req){
        .type = VIRTIO_SCSI_T_TMF,
        .subtype = VIRTIO_SCSI_T_TMF_LOGICAL_UNIT_RESET,
        .lun[0] = 1,
        .lun[1] = sc->device->id,
        .lun[2] = (sc->device->lun >> 8) | 0x40,
        .lun[3] = sc->device->lun & 0xff,
    };
    return virtscsi_tmf(vscsi, cmd);
}

static int virtscsi_abort(struct scsi_cmnd *sc)
{
    struct virtio_scsi *vscsi = shost_priv(sc->device->host);
    struct virtio_scsi_cmd *cmd;

    scmd_printk(KERN_INFO, sc, "abort\n");
    cmd = mempool_alloc(virtscsi_cmd_pool, GFP_NOIO);
    if (!cmd)
        return FAILED;

    memset(cmd, 0, sizeof(*cmd));
    cmd->sc = sc;
    cmd->req.tmf = (struct virtio_scsi_ctrl_tmf_req){
        .type = VIRTIO_SCSI_T_TMF,
        .subtype = VIRTIO_SCSI_T_TMF_ABORT_TASK,
        .lun[0] = 1,
        .lun[1] = sc->device->id,
        .lun[2] = (sc->device->lun >> 8) | 0x40,
        .lun[3] = sc->device->lun & 0xff,
        .tag = (unsigned long)sc,
    };
    return virtscsi_tmf(vscsi, cmd);
}

static struct scsi_host_template virtscsi_host_template = {
    .module = THIS_MODULE,
    .name = "Virtio SCSI HBA",
    .proc_name = "virtio_scsi",
    .queuecommand = virtscsi_queuecommand,
    .this_id = -1,
    .eh_abort_handler = virtscsi_abort,
    .eh_device_reset_handler = virtscsi_device_reset,

    .can_queue = 1024,
    .dma_boundary = UINT_MAX,
    .use_clustering = ENABLE_CLUSTERING,
};

#define virtscsi_config_get(vdev, fld) \
    ({ \
        typeof(((struct virtio_scsi_config *)0)->fld) __val; \
        vdev->config->get(vdev, \
                  offsetof(struct virtio_scsi_config, fld), \
                  &__val, sizeof(__val)); \
        __val; \
    })

#define virtscsi_config_set(vdev, fld, val) \
    (void)({ \
        typeof(((struct virtio_scsi_config *)0)->fld) __val = (val); \
        vdev->config->set(vdev, \
                  offsetof(struct virtio_scsi_config, fld), \
                  &__val, sizeof(__val)); \
    })

static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
                 struct virtqueue *vq)
{
    spin_lock_init(&virtscsi_vq->vq_lock);
    virtscsi_vq->vq = vq;
}

static struct virtio_scsi_target_state *virtscsi_alloc_tgt(
    struct virtio_device *vdev, int sg_elems)
{
    struct virtio_scsi_target_state *tgt;
    gfp_t gfp_mask = GFP_KERNEL;

    /* We need extra sg elements at head and tail.  */
    tgt = kmalloc(sizeof(*tgt) + sizeof(tgt->sg[0]) * (sg_elems + 2),
              gfp_mask);

    if (!tgt)
        return NULL;

    spin_lock_init(&tgt->tgt_lock);
    sg_init_table(tgt->sg, sg_elems + 2);
    return tgt;
}

static void virtscsi_scan(struct virtio_device *vdev)
{
    struct Scsi_Host *shost = (struct Scsi_Host *)vdev->priv;

    scsi_scan_host(shost);
}

static void virtscsi_remove_vqs(struct virtio_device *vdev)
{
    struct Scsi_Host *sh = virtio_scsi_host(vdev);
    struct virtio_scsi *vscsi = shost_priv(sh);
    u32 i, num_targets;

    /* Stop all the virtqueues. */
    vdev->config->reset(vdev);

    num_targets = sh->max_id;
    for (i = 0; i < num_targets; i++) {
        kfree(vscsi->tgt[i]);
        vscsi->tgt[i] = NULL;
    }

    vdev->config->del_vqs(vdev);
}

static int virtscsi_init(struct virtio_device *vdev,
             struct virtio_scsi *vscsi, int num_targets)
{
    int err;
    struct virtqueue *vqs[3];
    u32 i, sg_elems;

    vq_callback_t *callbacks[] = {
        virtscsi_ctrl_done,
        virtscsi_event_done,
        virtscsi_req_done
    };
    const char *names[] = {
        "control",
        "event",
        "request"
    };

    /* Discover virtqueues and write information to configuration.  */
    err = vdev->config->find_vqs(vdev, 3, vqs, callbacks, names);
    if (err)
        return err;

    virtscsi_init_vq(&vscsi->ctrl_vq, vqs[0]);
    virtscsi_init_vq(&vscsi->event_vq, vqs[1]);
    virtscsi_init_vq(&vscsi->req_vq, vqs[2]);

    virtscsi_config_set(vdev, cdb_size, VIRTIO_SCSI_CDB_SIZE);
    virtscsi_config_set(vdev, sense_size, VIRTIO_SCSI_SENSE_SIZE);

    if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
        virtscsi_kick_event_all(vscsi);

    /* We need to know how many segments before we allocate.  */
    sg_elems = virtscsi_config_get(vdev, seg_max) ?: 1;

    for (i = 0; i < num_targets; i++) {
        vscsi->tgt[i] = virtscsi_alloc_tgt(vdev, sg_elems);
        if (!vscsi->tgt[i]) {
            err = -ENOMEM;
            goto out;
        }
    }
    err = 0;

out:
    if (err)
        virtscsi_remove_vqs(vdev);
    return err;
}

static int __devinit virtscsi_probe(struct virtio_device *vdev)
{
    struct Scsi_Host *shost;
    struct virtio_scsi *vscsi;
    int err;
    u32 sg_elems, num_targets;
    u32 cmd_per_lun;

    /* Allocate memory and link the structs together.  */
    num_targets = virtscsi_config_get(vdev, max_target) + 1;
    shost = scsi_host_alloc(&virtscsi_host_template,
        sizeof(*vscsi)
        + num_targets * sizeof(struct virtio_scsi_target_state));

    if (!shost)
        return -ENOMEM;

    sg_elems = virtscsi_config_get(vdev, seg_max) ?: 1;
    shost->sg_tablesize = sg_elems;
    vscsi = shost_priv(shost);
    vscsi->vdev = vdev;
    vdev->priv = shost;

    err = virtscsi_init(vdev, vscsi, num_targets);
    if (err)
        goto virtscsi_init_failed;

    cmd_per_lun = virtscsi_config_get(vdev, cmd_per_lun) ?: 1;
    shost->cmd_per_lun = min_t(u32, cmd_per_lun, shost->can_queue);
    shost->max_sectors = virtscsi_config_get(vdev, max_sectors) ?: 0xFFFF;

    /* LUNs > 256 are reported with format 1, so they go in the range
     * 16640-32767.
     */
    shost->max_lun = virtscsi_config_get(vdev, max_lun) + 1 + 0x4000;
    shost->max_id = num_targets;
    shost->max_channel = 0;
    shost->max_cmd_len = VIRTIO_SCSI_CDB_SIZE;
    err = scsi_add_host(shost, &vdev->dev);
    if (err)
        goto scsi_add_host_failed;
    /*
     * scsi_scan_host() happens in virtscsi_scan() via virtio_driver->scan()
     * after VIRTIO_CONFIG_S_DRIVER_OK has been set..
     */
    return 0;

scsi_add_host_failed:
    vdev->config->del_vqs(vdev);
virtscsi_init_failed:
    scsi_host_put(shost);
    return err;
}

static void __devexit virtscsi_remove(struct virtio_device *vdev)
{
    struct Scsi_Host *shost = virtio_scsi_host(vdev);
    struct virtio_scsi *vscsi = shost_priv(shost);

    if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
        virtscsi_cancel_event_work(vscsi);

    scsi_remove_host(shost);

    virtscsi_remove_vqs(vdev);
    scsi_host_put(shost);
}

#ifdef CONFIG_PM
static int virtscsi_freeze(struct virtio_device *vdev)
{
    virtscsi_remove_vqs(vdev);
    return 0;
}

static int virtscsi_restore(struct virtio_device *vdev)
{
    struct Scsi_Host *sh = virtio_scsi_host(vdev);
    struct virtio_scsi *vscsi = shost_priv(sh);

    return virtscsi_init(vdev, vscsi, sh->max_id);
}
#endif

static struct virtio_device_id id_table[] = {
    { VIRTIO_ID_SCSI, VIRTIO_DEV_ANY_ID },
    { 0 },
};

static unsigned int features[] = {
    VIRTIO_SCSI_F_HOTPLUG,
    VIRTIO_SCSI_F_CHANGE,
};

static struct virtio_driver virtio_scsi_driver = {
    .feature_table = features,
    .feature_table_size = ARRAY_SIZE(features),
    .driver.name = KBUILD_MODNAME,
    .driver.owner = THIS_MODULE,
    .id_table = id_table,
    .probe = virtscsi_probe,
    .scan = virtscsi_scan,
#ifdef CONFIG_PM
    .freeze = virtscsi_freeze,
    .restore = virtscsi_restore,
#endif
    .remove = __devexit_p(virtscsi_remove),
};

static int __init init(void)
{
    int ret = -ENOMEM;

    virtscsi_cmd_cache = KMEM_CACHE(virtio_scsi_cmd, 0);
    if (!virtscsi_cmd_cache) {
        printk(KERN_ERR "kmem_cache_create() for "
                "virtscsi_cmd_cache failed\n");
        goto error;
    }


    virtscsi_cmd_pool =
        mempool_create_slab_pool(VIRTIO_SCSI_MEMPOOL_SZ,
                     virtscsi_cmd_cache);
    if (!virtscsi_cmd_pool) {
        printk(KERN_ERR "mempool_create() for"
                "virtscsi_cmd_pool failed\n");
        goto error;
    }
    ret = register_virtio_driver(&virtio_scsi_driver);
    if (ret < 0)
        goto error;

    return 0;

error:
    if (virtscsi_cmd_pool) {
        mempool_destroy(virtscsi_cmd_pool);
        virtscsi_cmd_pool = NULL;
    }
    if (virtscsi_cmd_cache) {
        kmem_cache_destroy(virtscsi_cmd_cache);
        virtscsi_cmd_cache = NULL;
    }
    return ret;
}

static void __exit fini(void)
{
    unregister_virtio_driver(&virtio_scsi_driver);
    mempool_destroy(virtscsi_cmd_pool);
    kmem_cache_destroy(virtscsi_cmd_cache);
}
module_init(init);
module_exit(fini);

MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio SCSI HBA driver");
MODULE_LICENSE("GPL");