// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Virtio SCSI HBA driver
 *
 * Copyright IBM Corp. 2010
 * Copyright Red Hat, Inc. 2011
 *
 * Authors:
 *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
 *  Paolo Bonzini   <pbonzini@redhat.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/mempool.h>
#include <linux/interrupt.h>
#include <linux/virtio.h>
#include <linux/virtio_ids.h>
#include <linux/virtio_config.h>
#include <linux/virtio_scsi.h>
#include <linux/cpu.h>
#include <linux/blkdev.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_tcq.h>
#include <scsi/scsi_devinfo.h>
#include <linux/seqlock.h>
#include <linux/blk-mq-virtio.h>

#include "sd.h"

#define VIRTIO_SCSI_MEMPOOL_SZ 64
#define VIRTIO_SCSI_EVENT_LEN 8
#define VIRTIO_SCSI_VQ_BASE 2

/* Command queue element */
struct virtio_scsi_cmd {
        struct scsi_cmnd *sc;
        struct completion *comp;
        union {
                struct virtio_scsi_cmd_req       cmd;
                struct virtio_scsi_cmd_req_pi    cmd_pi;
                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;
};

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

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

        u32 num_queues;

        struct hlist_node node;

        /* Protected by event_vq lock */
        bool stop_events;

        struct virtio_scsi_vq ctrl_vq;
        struct virtio_scsi_vq event_vq;
        struct virtio_scsi_vq req_vqs[];
};

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)
                scsi_set_resid(sc, resid);
}

/*
 * virtscsi_complete_cmd - finish a scsi_cmd and invoke scsi_done
 *
 * Called with vq_lock held.
 */
static void virtscsi_complete_cmd(struct virtio_scsi *vscsi, 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, virtio32_to_cpu(vscsi->vdev, 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);
                fallthrough;
        case VIRTIO_SCSI_S_FAILURE:
                set_host_byte(sc, DID_ERROR);
                break;
        }

        WARN_ON(virtio32_to_cpu(vscsi->vdev, resp->sense_len) >
                VIRTIO_SCSI_SENSE_SIZE);
        if (sc->sense_buffer) {
                memcpy(sc->sense_buffer, resp->sense,
                       min_t(u32,
                             virtio32_to_cpu(vscsi->vdev, resp->sense_len),
                             VIRTIO_SCSI_SENSE_SIZE));
                if (resp->sense_len)
                        set_driver_byte(sc, DRIVER_SENSE);
        }

        sc->scsi_done(sc);
}

static void virtscsi_vq_done(struct virtio_scsi *vscsi,
                             struct virtio_scsi_vq *virtscsi_vq,
                             void (*fn)(struct virtio_scsi *vscsi, void *buf))
{
        void *buf;
        unsigned int len;
        unsigned long flags;
        struct virtqueue *vq = virtscsi_vq->vq;

        spin_lock_irqsave(&virtscsi_vq->vq_lock, flags);
        do {
                virtqueue_disable_cb(vq);
                while ((buf = virtqueue_get_buf(vq, &len)) != NULL)
                        fn(vscsi, buf);

                if (unlikely(virtqueue_is_broken(vq)))
                        break;
        } while (!virtqueue_enable_cb(vq));
        spin_unlock_irqrestore(&virtscsi_vq->vq_lock, flags);
}

static void virtscsi_req_done(struct virtqueue *vq)
{
        struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
        struct virtio_scsi *vscsi = shost_priv(sh);
        int index = vq->index - VIRTIO_SCSI_VQ_BASE;
        struct virtio_scsi_vq *req_vq = &vscsi->req_vqs[index];

        virtscsi_vq_done(vscsi, req_vq, virtscsi_complete_cmd);
};

static void virtscsi_poll_requests(struct virtio_scsi *vscsi)
{
        int i, num_vqs;

        num_vqs = vscsi->num_queues;
        for (i = 0; i < num_vqs; i++)
                virtscsi_vq_done(vscsi, &vscsi->req_vqs[i],
                                 virtscsi_complete_cmd);
}

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

        if (cmd->comp)
                complete(cmd->comp);
}

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

        virtscsi_vq_done(vscsi, &vscsi->ctrl_vq, virtscsi_complete_free);
};

static void virtscsi_handle_event(struct work_struct *work);

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

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

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

        err = virtqueue_add_inbuf(vscsi->event_vq.vq, &sg, 1, event_node,
                                  GFP_ATOMIC);
        if (!err)
                virtqueue_kick(vscsi->event_vq.vq);

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

        return err;
}

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;

        /* Stop scheduling work before calling cancel_work_sync.  */
        spin_lock_irq(&vscsi->event_vq.vq_lock);
        vscsi->stop_events = true;
        spin_unlock_irq(&vscsi->event_vq.vq_lock);

        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 (virtio32_to_cpu(vscsi->vdev, event->reason)) {
        case VIRTIO_SCSI_EVT_RESET_RESCAN:
                if (lun == 0) {
                        scsi_scan_target(&shost->shost_gendev, 0, target,
                                         SCAN_WILD_CARD, SCSI_SCAN_INITIAL);
                } else {
                        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 = virtio32_to_cpu(vscsi->vdev, event->reason) & 255;
        u8 ascq = virtio32_to_cpu(vscsi->vdev, 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_rescan_hotunplug(struct virtio_scsi *vscsi)
{
        struct scsi_device *sdev;
        struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
        unsigned char scsi_cmd[MAX_COMMAND_SIZE];
        int result, inquiry_len, inq_result_len = 256;
        char *inq_result = kmalloc(inq_result_len, GFP_KERNEL);

        shost_for_each_device(sdev, shost) {
                inquiry_len = sdev->inquiry_len ? sdev->inquiry_len : 36;

                memset(scsi_cmd, 0, sizeof(scsi_cmd));
                scsi_cmd[0] = INQUIRY;
                scsi_cmd[4] = (unsigned char) inquiry_len;

                memset(inq_result, 0, inq_result_len);

                result = scsi_execute_req(sdev, scsi_cmd, DMA_FROM_DEVICE,
                                          inq_result, inquiry_len, NULL,
                                          SD_TIMEOUT, SD_MAX_RETRIES, NULL);

                if (result == 0 && inq_result[0] >> 5) {
                        /* PQ indicates the LUN is not attached */
                        scsi_remove_device(sdev);
                } else if (host_byte(result) == DID_BAD_TARGET) {
                        /*
                         * If all LUNs of a virtio-scsi device are unplugged
                         * it will respond with BAD TARGET on any INQUIRY
                         * command.
                         * Remove the device in this case as well.
                         */
                        scsi_remove_device(sdev);
                }
        }

        kfree(inq_result);
}

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 &
            cpu_to_virtio32(vscsi->vdev, VIRTIO_SCSI_T_EVENTS_MISSED)) {
                event->event &= ~cpu_to_virtio32(vscsi->vdev,
                                                   VIRTIO_SCSI_T_EVENTS_MISSED);
                virtscsi_rescan_hotunplug(vscsi);
                scsi_scan_host(virtio_scsi_host(vscsi->vdev));
        }

        switch (virtio32_to_cpu(vscsi->vdev, 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(struct virtio_scsi *vscsi, void *buf)
{
        struct virtio_scsi_event_node *event_node = buf;

        if (!vscsi->stop_events)
                queue_work(system_freezable_wq, &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);

        virtscsi_vq_done(vscsi, &vscsi->event_vq, virtscsi_complete_event);
};

static int __virtscsi_add_cmd(struct virtqueue *vq,
                            struct virtio_scsi_cmd *cmd,
                            size_t req_size, size_t resp_size)
{
        struct scsi_cmnd *sc = cmd->sc;
        struct scatterlist *sgs[6], req, resp;
        struct sg_table *out, *in;
        unsigned out_num = 0, in_num = 0;

        out = in = NULL;

        if (sc && sc->sc_data_direction != DMA_NONE) {
                if (sc->sc_data_direction != DMA_FROM_DEVICE)
                        out = &sc->sdb.table;
                if (sc->sc_data_direction != DMA_TO_DEVICE)
                        in = &sc->sdb.table;
        }

        /* Request header.  */
        sg_init_one(&req, &cmd->req, req_size);
        sgs[out_num++] = &req;

        /* Data-out buffer.  */
        if (out) {
                /* Place WRITE protection SGLs before Data OUT payload */
                if (scsi_prot_sg_count(sc))
                        sgs[out_num++] = scsi_prot_sglist(sc);
                sgs[out_num++] = out->sgl;
        }

        /* Response header.  */
        sg_init_one(&resp, &cmd->resp, resp_size);
        sgs[out_num + in_num++] = &resp;

        /* Data-in buffer */
        if (in) {
                /* Place READ protection SGLs before Data IN payload */
                if (scsi_prot_sg_count(sc))
                        sgs[out_num + in_num++] = scsi_prot_sglist(sc);
                sgs[out_num + in_num++] = in->sgl;
        }

        return virtqueue_add_sgs(vq, sgs, out_num, in_num, cmd, GFP_ATOMIC);
}

static void virtscsi_kick_vq(struct virtio_scsi_vq *vq)
{
        bool needs_kick;
        unsigned long flags;

        spin_lock_irqsave(&vq->vq_lock, flags);
        needs_kick = virtqueue_kick_prepare(vq->vq);
        spin_unlock_irqrestore(&vq->vq_lock, flags);

        if (needs_kick)
                virtqueue_notify(vq->vq);
}

/**
 * virtscsi_add_cmd - add a virtio_scsi_cmd to a virtqueue, optionally kick it
 * @vq          : the struct virtqueue we're talking about
 * @cmd         : command structure
 * @req_size    : size of the request buffer
 * @resp_size   : size of the response buffer
 * @kick        : whether to kick the virtqueue immediately
 */
static int virtscsi_add_cmd(struct virtio_scsi_vq *vq,
                             struct virtio_scsi_cmd *cmd,
                             size_t req_size, size_t resp_size,
                             bool kick)
{
        unsigned long flags;
        int err;
        bool needs_kick = false;

        spin_lock_irqsave(&vq->vq_lock, flags);
        err = __virtscsi_add_cmd(vq->vq, cmd, req_size, resp_size);
        if (!err && kick)
                needs_kick = virtqueue_kick_prepare(vq->vq);

        spin_unlock_irqrestore(&vq->vq_lock, flags);

        if (needs_kick)
                virtqueue_notify(vq->vq);
        return err;
}

static void virtio_scsi_init_hdr(struct virtio_device *vdev,
                                 struct virtio_scsi_cmd_req *cmd,
                                 struct scsi_cmnd *sc)
{
        cmd->lun[0] = 1;
        cmd->lun[1] = sc->device->id;
        cmd->lun[2] = (sc->device->lun >> 8) | 0x40;
        cmd->lun[3] = sc->device->lun & 0xff;
        cmd->tag = cpu_to_virtio64(vdev, (unsigned long)sc);
        cmd->task_attr = VIRTIO_SCSI_S_SIMPLE;
        cmd->prio = 0;
        cmd->crn = 0;
}

#ifdef CONFIG_BLK_DEV_INTEGRITY
static void virtio_scsi_init_hdr_pi(struct virtio_device *vdev,
                                    struct virtio_scsi_cmd_req_pi *cmd_pi,
                                    struct scsi_cmnd *sc)
{
        struct request *rq = sc->request;
        struct blk_integrity *bi;

        virtio_scsi_init_hdr(vdev, (struct virtio_scsi_cmd_req *)cmd_pi, sc);

        if (!rq || !scsi_prot_sg_count(sc))
                return;

        bi = blk_get_integrity(rq->rq_disk);

        if (sc->sc_data_direction == DMA_TO_DEVICE)
                cmd_pi->pi_bytesout = cpu_to_virtio32(vdev,
                                                      bio_integrity_bytes(bi,
                                                        blk_rq_sectors(rq)));
        else if (sc->sc_data_direction == DMA_FROM_DEVICE)
                cmd_pi->pi_bytesin = cpu_to_virtio32(vdev,
                                                     bio_integrity_bytes(bi,
                                                        blk_rq_sectors(rq)));
}
#endif

static struct virtio_scsi_vq *virtscsi_pick_vq_mq(struct virtio_scsi *vscsi,
                                                  struct scsi_cmnd *sc)
{
        u32 tag = blk_mq_unique_tag(sc->request);
        u16 hwq = blk_mq_unique_tag_to_hwq(tag);

        return &vscsi->req_vqs[hwq];
}

static int virtscsi_queuecommand(struct Scsi_Host *shost,
                                 struct scsi_cmnd *sc)
{
        struct virtio_scsi *vscsi = shost_priv(shost);
        struct virtio_scsi_vq *req_vq = virtscsi_pick_vq_mq(vscsi, sc);
        struct virtio_scsi_cmd *cmd = scsi_cmd_priv(sc);
        bool kick;
        unsigned long flags;
        int req_size;
        int ret;

        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]);

        cmd->sc = sc;

        BUG_ON(sc->cmd_len > VIRTIO_SCSI_CDB_SIZE);

#ifdef CONFIG_BLK_DEV_INTEGRITY
        if (virtio_has_feature(vscsi->vdev, VIRTIO_SCSI_F_T10_PI)) {
                virtio_scsi_init_hdr_pi(vscsi->vdev, &cmd->req.cmd_pi, sc);
                memcpy(cmd->req.cmd_pi.cdb, sc->cmnd, sc->cmd_len);
                req_size = sizeof(cmd->req.cmd_pi);
        } else
#endif
        {
                virtio_scsi_init_hdr(vscsi->vdev, &cmd->req.cmd, sc);
                memcpy(cmd->req.cmd.cdb, sc->cmnd, sc->cmd_len);
                req_size = sizeof(cmd->req.cmd);
        }

        kick = (sc->flags & SCMD_LAST) != 0;
        ret = virtscsi_add_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd), kick);
        if (ret == -EIO) {
                cmd->resp.cmd.response = VIRTIO_SCSI_S_BAD_TARGET;
                spin_lock_irqsave(&req_vq->vq_lock, flags);
                virtscsi_complete_cmd(vscsi, cmd);
                spin_unlock_irqrestore(&req_vq->vq_lock, flags);
        } else if (ret != 0) {
                return SCSI_MLQUEUE_HOST_BUSY;
        }
        return 0;
}

static int virtscsi_tmf(struct virtio_scsi *vscsi, struct virtio_scsi_cmd *cmd)
{
        DECLARE_COMPLETION_ONSTACK(comp);
        int ret = FAILED;

        cmd->comp = &comp;
        if (virtscsi_add_cmd(&vscsi->ctrl_vq, cmd,
                              sizeof cmd->req.tmf, sizeof cmd->resp.tmf, true) < 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;

        /*
         * The spec guarantees that all requests related to the TMF have
         * been completed, but the callback might not have run yet if
         * we're using independent interrupts (e.g. MSI).  Poll the
         * virtqueues once.
         *
         * In the abort case, sc->scsi_done will do nothing, because
         * the block layer must have detected a timeout and as a result
         * REQ_ATOM_COMPLETE has been set.
         */
        virtscsi_poll_requests(vscsi);

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->req.tmf = (struct virtio_scsi_ctrl_tmf_req){
                .type = VIRTIO_SCSI_T_TMF,
                .subtype = cpu_to_virtio32(vscsi->vdev,
                                             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_device_alloc(struct scsi_device *sdevice)
{
        /*
         * Passed through SCSI targets (e.g. with qemu's 'scsi-block')
         * may have transfer limits which come from the host SCSI
         * controller or something on the host side other than the
         * target itself.
         *
         * To make this work properly, the hypervisor can adjust the
         * target's VPD information to advertise these limits.  But
         * for that to work, the guest has to look at the VPD pages,
         * which we won't do by default if it is an SPC-2 device, even
         * if it does actually support it.
         *
         * So, set the blist to always try to read the VPD pages.
         */
        sdevice->sdev_bflags = BLIST_TRY_VPD_PAGES;

        return 0;
}


/**
 * virtscsi_change_queue_depth() - Change a virtscsi target's queue depth
 * @sdev:       Virtscsi target whose queue depth to change
 * @qdepth:     New queue depth
 */
static int virtscsi_change_queue_depth(struct scsi_device *sdev, int qdepth)
{
        struct Scsi_Host *shost = sdev->host;
        int max_depth = shost->cmd_per_lun;

        return scsi_change_queue_depth(sdev, min(max_depth, qdepth));
}

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->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 = cpu_to_virtio64(vscsi->vdev, (unsigned long)sc),
        };
        return virtscsi_tmf(vscsi, cmd);
}

static int virtscsi_map_queues(struct Scsi_Host *shost)
{
        struct virtio_scsi *vscsi = shost_priv(shost);
        struct blk_mq_queue_map *qmap = &shost->tag_set.map[HCTX_TYPE_DEFAULT];

        return blk_mq_virtio_map_queues(qmap, vscsi->vdev, 2);
}

static void virtscsi_commit_rqs(struct Scsi_Host *shost, u16 hwq)
{
        struct virtio_scsi *vscsi = shost_priv(shost);

        virtscsi_kick_vq(&vscsi->req_vqs[hwq]);
}

/*
 * The host guarantees to respond to each command, although I/O
 * latencies might be higher than on bare metal.  Reset the timer
 * unconditionally to give the host a chance to perform EH.
 */
static enum blk_eh_timer_return virtscsi_eh_timed_out(struct scsi_cmnd *scmnd)
{
        return BLK_EH_RESET_TIMER;
}

static struct scsi_host_template virtscsi_host_template = {
        .module = THIS_MODULE,
        .name = "Virtio SCSI HBA",
        .proc_name = "virtio_scsi",
        .this_id = -1,
        .cmd_size = sizeof(struct virtio_scsi_cmd),
        .queuecommand = virtscsi_queuecommand,
        .commit_rqs = virtscsi_commit_rqs,
        .change_queue_depth = virtscsi_change_queue_depth,
        .eh_abort_handler = virtscsi_abort,
        .eh_device_reset_handler = virtscsi_device_reset,
        .eh_timed_out = virtscsi_eh_timed_out,
        .slave_alloc = virtscsi_device_alloc,

        .dma_boundary = UINT_MAX,
        .map_queues = virtscsi_map_queues,
        .track_queue_depth = 1,
};

#define virtscsi_config_get(vdev, fld) \
        ({ \
                __virtio_native_type(struct virtio_scsi_config, fld) __val; \
                virtio_cread(vdev, struct virtio_scsi_config, fld, &__val); \
                __val; \
        })

#define virtscsi_config_set(vdev, fld, val) \
        do { \
                __virtio_native_type(struct virtio_scsi_config, fld) __val = (val); \
                virtio_cwrite(vdev, struct virtio_scsi_config, fld, &__val); \
        } while(0)

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 void virtscsi_remove_vqs(struct virtio_device *vdev)
{
        /* Stop all the virtqueues. */
        vdev->config->reset(vdev);
        vdev->config->del_vqs(vdev);
}

static int virtscsi_init(struct virtio_device *vdev,
                         struct virtio_scsi *vscsi)
{
        int err;
        u32 i;
        u32 num_vqs;
        vq_callback_t **callbacks;
        const char **names;
        struct virtqueue **vqs;
        struct irq_affinity desc = { .pre_vectors = 2 };

        num_vqs = vscsi->num_queues + VIRTIO_SCSI_VQ_BASE;
        vqs = kmalloc_array(num_vqs, sizeof(struct virtqueue *), GFP_KERNEL);
        callbacks = kmalloc_array(num_vqs, sizeof(vq_callback_t *),
                                  GFP_KERNEL);
        names = kmalloc_array(num_vqs, sizeof(char *), GFP_KERNEL);

        if (!callbacks || !vqs || !names) {
                err = -ENOMEM;
                goto out;
        }

        callbacks[0] = virtscsi_ctrl_done;
        callbacks[1] = virtscsi_event_done;
        names[0] = "control";
        names[1] = "event";
        for (i = VIRTIO_SCSI_VQ_BASE; i < num_vqs; i++) {
                callbacks[i] = virtscsi_req_done;
                names[i] = "request";
        }

        /* Discover virtqueues and write information to configuration.  */
        err = virtio_find_vqs(vdev, num_vqs, vqs, callbacks, names, &desc);
        if (err)
                goto out;

        virtscsi_init_vq(&vscsi->ctrl_vq, vqs[0]);
        virtscsi_init_vq(&vscsi->event_vq, vqs[1]);
        for (i = VIRTIO_SCSI_VQ_BASE; i < num_vqs; i++)
                virtscsi_init_vq(&vscsi->req_vqs[i - VIRTIO_SCSI_VQ_BASE],
                                 vqs[i]);

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

        err = 0;

out:
        kfree(names);
        kfree(callbacks);
        kfree(vqs);
        if (err)
                virtscsi_remove_vqs(vdev);
        return err;
}

static int 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;
        u32 num_queues;

        if (!vdev->config->get) {
                dev_err(&vdev->dev, "%s failure: config access disabled\n",
                        __func__);
                return -EINVAL;
        }

        /* We need to know how many queues before we allocate. */
        num_queues = virtscsi_config_get(vdev, num_queues) ? : 1;
        num_queues = min_t(unsigned int, nr_cpu_ids, num_queues);

        num_targets = virtscsi_config_get(vdev, max_target) + 1;

        shost = scsi_host_alloc(&virtscsi_host_template,
                                struct_size(vscsi, req_vqs, num_queues));
        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;
        vscsi->num_queues = num_queues;
        vdev->priv = shost;

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

        shost->can_queue = virtqueue_get_vring_size(vscsi->req_vqs[0].vq);

        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;
        shost->nr_hw_queues = num_queues;

#ifdef CONFIG_BLK_DEV_INTEGRITY
        if (virtio_has_feature(vdev, VIRTIO_SCSI_F_T10_PI)) {
                int host_prot;

                host_prot = SHOST_DIF_TYPE1_PROTECTION | SHOST_DIF_TYPE2_PROTECTION |
                            SHOST_DIF_TYPE3_PROTECTION | SHOST_DIX_TYPE1_PROTECTION |
                            SHOST_DIX_TYPE2_PROTECTION | SHOST_DIX_TYPE3_PROTECTION;

                scsi_host_set_prot(shost, host_prot);
                scsi_host_set_guard(shost, SHOST_DIX_GUARD_CRC);
        }
#endif

        err = scsi_add_host(shost, &vdev->dev);
        if (err)
                goto scsi_add_host_failed;

        virtio_device_ready(vdev);

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

        scsi_scan_host(shost);
        return 0;

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

static void 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_SLEEP
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);
        int err;

        err = virtscsi_init(vdev, vscsi);
        if (err)
                return err;

        virtio_device_ready(vdev);

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

        return err;
}
#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,
#ifdef CONFIG_BLK_DEV_INTEGRITY
        VIRTIO_SCSI_F_T10_PI,
#endif
};

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,
#ifdef CONFIG_PM_SLEEP
        .freeze = virtscsi_freeze,
        .restore = virtscsi_restore,
#endif
        .remove = virtscsi_remove,
};

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

        virtscsi_cmd_cache = KMEM_CACHE(virtio_scsi_cmd, 0);
        if (!virtscsi_cmd_cache) {
                pr_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) {
                pr_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:
        mempool_destroy(virtscsi_cmd_pool);
        virtscsi_cmd_pool = NULL;
        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");