of: MSI: Simplify irqdomain lookup

[linux/fpc-iii.git] / drivers / scsi / storvsc_drv.c

/*
 * Copyright (c) 2009, Microsoft Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307 USA.
 *
 * Authors:
 *   Haiyang Zhang <haiyangz@microsoft.com>
 *   Hank Janssen  <hjanssen@microsoft.com>
 *   K. Y. Srinivasan <kys@microsoft.com>
 */

#include <linux/kernel.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/completion.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/hyperv.h>
#include <linux/blkdev.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_tcq.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_devinfo.h>
#include <scsi/scsi_dbg.h>

/*
 * All wire protocol details (storage protocol between the guest and the host)
 * are consolidated here.
 *
 * Begin protocol definitions.
 */

/*
 * Version history:
 * V1 Beta: 0.1
 * V1 RC < 2008/1/31: 1.0
 * V1 RC > 2008/1/31:  2.0
 * Win7: 4.2
 * Win8: 5.1
 * Win8.1: 6.0
 * Win10: 6.2
 */

#define VMSTOR_PROTO_VERSION(MAJOR_, MINOR_)    ((((MAJOR_) & 0xff) << 8) | \
                                                (((MINOR_) & 0xff)))

#define VMSTOR_PROTO_VERSION_WIN6       VMSTOR_PROTO_VERSION(2, 0)
#define VMSTOR_PROTO_VERSION_WIN7       VMSTOR_PROTO_VERSION(4, 2)
#define VMSTOR_PROTO_VERSION_WIN8       VMSTOR_PROTO_VERSION(5, 1)
#define VMSTOR_PROTO_VERSION_WIN8_1     VMSTOR_PROTO_VERSION(6, 0)
#define VMSTOR_PROTO_VERSION_WIN10      VMSTOR_PROTO_VERSION(6, 2)

/*  Packet structure describing virtual storage requests. */
enum vstor_packet_operation {
        VSTOR_OPERATION_COMPLETE_IO             = 1,
        VSTOR_OPERATION_REMOVE_DEVICE           = 2,
        VSTOR_OPERATION_EXECUTE_SRB             = 3,
        VSTOR_OPERATION_RESET_LUN               = 4,
        VSTOR_OPERATION_RESET_ADAPTER           = 5,
        VSTOR_OPERATION_RESET_BUS               = 6,
        VSTOR_OPERATION_BEGIN_INITIALIZATION    = 7,
        VSTOR_OPERATION_END_INITIALIZATION      = 8,
        VSTOR_OPERATION_QUERY_PROTOCOL_VERSION  = 9,
        VSTOR_OPERATION_QUERY_PROPERTIES        = 10,
        VSTOR_OPERATION_ENUMERATE_BUS           = 11,
        VSTOR_OPERATION_FCHBA_DATA              = 12,
        VSTOR_OPERATION_CREATE_SUB_CHANNELS     = 13,
        VSTOR_OPERATION_MAXIMUM                 = 13
};

/*
 * WWN packet for Fibre Channel HBA
 */

struct hv_fc_wwn_packet {
        bool    primary_active;
        u8      reserved1;
        u8      reserved2;
        u8      primary_port_wwn[8];
        u8      primary_node_wwn[8];
        u8      secondary_port_wwn[8];
        u8      secondary_node_wwn[8];
};



/*
 * SRB Flag Bits
 */

#define SRB_FLAGS_QUEUE_ACTION_ENABLE           0x00000002
#define SRB_FLAGS_DISABLE_DISCONNECT            0x00000004
#define SRB_FLAGS_DISABLE_SYNCH_TRANSFER        0x00000008
#define SRB_FLAGS_BYPASS_FROZEN_QUEUE           0x00000010
#define SRB_FLAGS_DISABLE_AUTOSENSE             0x00000020
#define SRB_FLAGS_DATA_IN                       0x00000040
#define SRB_FLAGS_DATA_OUT                      0x00000080
#define SRB_FLAGS_NO_DATA_TRANSFER              0x00000000
#define SRB_FLAGS_UNSPECIFIED_DIRECTION (SRB_FLAGS_DATA_IN | SRB_FLAGS_DATA_OUT)
#define SRB_FLAGS_NO_QUEUE_FREEZE               0x00000100
#define SRB_FLAGS_ADAPTER_CACHE_ENABLE          0x00000200
#define SRB_FLAGS_FREE_SENSE_BUFFER             0x00000400

/*
 * This flag indicates the request is part of the workflow for processing a D3.
 */
#define SRB_FLAGS_D3_PROCESSING                 0x00000800
#define SRB_FLAGS_IS_ACTIVE                     0x00010000
#define SRB_FLAGS_ALLOCATED_FROM_ZONE           0x00020000
#define SRB_FLAGS_SGLIST_FROM_POOL              0x00040000
#define SRB_FLAGS_BYPASS_LOCKED_QUEUE           0x00080000
#define SRB_FLAGS_NO_KEEP_AWAKE                 0x00100000
#define SRB_FLAGS_PORT_DRIVER_ALLOCSENSE        0x00200000
#define SRB_FLAGS_PORT_DRIVER_SENSEHASPORT      0x00400000
#define SRB_FLAGS_DONT_START_NEXT_PACKET        0x00800000
#define SRB_FLAGS_PORT_DRIVER_RESERVED          0x0F000000
#define SRB_FLAGS_CLASS_DRIVER_RESERVED         0xF0000000


/*
 * Platform neutral description of a scsi request -
 * this remains the same across the write regardless of 32/64 bit
 * note: it's patterned off the SCSI_PASS_THROUGH structure
 */
#define STORVSC_MAX_CMD_LEN                     0x10

#define POST_WIN7_STORVSC_SENSE_BUFFER_SIZE     0x14
#define PRE_WIN8_STORVSC_SENSE_BUFFER_SIZE      0x12

#define STORVSC_SENSE_BUFFER_SIZE               0x14
#define STORVSC_MAX_BUF_LEN_WITH_PADDING        0x14

/*
 * Sense buffer size changed in win8; have a run-time
 * variable to track the size we should use.  This value will
 * likely change during protocol negotiation but it is valid
 * to start by assuming pre-Win8.
 */
static int sense_buffer_size = PRE_WIN8_STORVSC_SENSE_BUFFER_SIZE;

/*
 * The storage protocol version is determined during the
 * initial exchange with the host.  It will indicate which
 * storage functionality is available in the host.
*/
static int vmstor_proto_version;

struct vmscsi_win8_extension {
        /*
         * The following were added in Windows 8
         */
        u16 reserve;
        u8  queue_tag;
        u8  queue_action;
        u32 srb_flags;
        u32 time_out_value;
        u32 queue_sort_ey;
} __packed;

struct vmscsi_request {
        u16 length;
        u8 srb_status;
        u8 scsi_status;

        u8  port_number;
        u8  path_id;
        u8  target_id;
        u8  lun;

        u8  cdb_length;
        u8  sense_info_length;
        u8  data_in;
        u8  reserved;

        u32 data_transfer_length;

        union {
                u8 cdb[STORVSC_MAX_CMD_LEN];
                u8 sense_data[STORVSC_SENSE_BUFFER_SIZE];
                u8 reserved_array[STORVSC_MAX_BUF_LEN_WITH_PADDING];
        };
        /*
         * The following was added in win8.
         */
        struct vmscsi_win8_extension win8_extension;

} __attribute((packed));


/*
 * The size of the vmscsi_request has changed in win8. The
 * additional size is because of new elements added to the
 * structure. These elements are valid only when we are talking
 * to a win8 host.
 * Track the correction to size we need to apply. This value
 * will likely change during protocol negotiation but it is
 * valid to start by assuming pre-Win8.
 */
static int vmscsi_size_delta = sizeof(struct vmscsi_win8_extension);

/*
 * The list of storage protocols in order of preference.
 */
struct vmstor_protocol {
        int protocol_version;
        int sense_buffer_size;
        int vmscsi_size_delta;
};


static const struct vmstor_protocol vmstor_protocols[] = {
        {
                VMSTOR_PROTO_VERSION_WIN10,
                POST_WIN7_STORVSC_SENSE_BUFFER_SIZE,
                0
        },
        {
                VMSTOR_PROTO_VERSION_WIN8_1,
                POST_WIN7_STORVSC_SENSE_BUFFER_SIZE,
                0
        },
        {
                VMSTOR_PROTO_VERSION_WIN8,
                POST_WIN7_STORVSC_SENSE_BUFFER_SIZE,
                0
        },
        {
                VMSTOR_PROTO_VERSION_WIN7,
                PRE_WIN8_STORVSC_SENSE_BUFFER_SIZE,
                sizeof(struct vmscsi_win8_extension),
        },
        {
                VMSTOR_PROTO_VERSION_WIN6,
                PRE_WIN8_STORVSC_SENSE_BUFFER_SIZE,
                sizeof(struct vmscsi_win8_extension),
        }
};


/*
 * This structure is sent during the intialization phase to get the different
 * properties of the channel.
 */

#define STORAGE_CHANNEL_SUPPORTS_MULTI_CHANNEL          0x1

struct vmstorage_channel_properties {
        u32 reserved;
        u16 max_channel_cnt;
        u16 reserved1;

        u32 flags;
        u32   max_transfer_bytes;

        u64  reserved2;
} __packed;

/*  This structure is sent during the storage protocol negotiations. */
struct vmstorage_protocol_version {
        /* Major (MSW) and minor (LSW) version numbers. */
        u16 major_minor;

        /*
         * Revision number is auto-incremented whenever this file is changed
         * (See FILL_VMSTOR_REVISION macro above).  Mismatch does not
         * definitely indicate incompatibility--but it does indicate mismatched
         * builds.
         * This is only used on the windows side. Just set it to 0.
         */
        u16 revision;
} __packed;

/* Channel Property Flags */
#define STORAGE_CHANNEL_REMOVABLE_FLAG          0x1
#define STORAGE_CHANNEL_EMULATED_IDE_FLAG       0x2

struct vstor_packet {
        /* Requested operation type */
        enum vstor_packet_operation operation;

        /*  Flags - see below for values */
        u32 flags;

        /* Status of the request returned from the server side. */
        u32 status;

        /* Data payload area */
        union {
                /*
                 * Structure used to forward SCSI commands from the
                 * client to the server.
                 */
                struct vmscsi_request vm_srb;

                /* Structure used to query channel properties. */
                struct vmstorage_channel_properties storage_channel_properties;

                /* Used during version negotiations. */
                struct vmstorage_protocol_version version;

                /* Fibre channel address packet */
                struct hv_fc_wwn_packet wwn_packet;

                /* Number of sub-channels to create */
                u16 sub_channel_count;

                /* This will be the maximum of the union members */
                u8  buffer[0x34];
        };
} __packed;

/*
 * Packet Flags:
 *
 * This flag indicates that the server should send back a completion for this
 * packet.
 */

#define REQUEST_COMPLETION_FLAG 0x1

/* Matches Windows-end */
enum storvsc_request_type {
        WRITE_TYPE = 0,
        READ_TYPE,
        UNKNOWN_TYPE,
};

/*
 * SRB status codes and masks; a subset of the codes used here.
 */

#define SRB_STATUS_AUTOSENSE_VALID      0x80
#define SRB_STATUS_QUEUE_FROZEN         0x40
#define SRB_STATUS_INVALID_LUN  0x20
#define SRB_STATUS_SUCCESS      0x01
#define SRB_STATUS_ABORTED      0x02
#define SRB_STATUS_ERROR        0x04

#define SRB_STATUS(status) \
        (status & ~(SRB_STATUS_AUTOSENSE_VALID | SRB_STATUS_QUEUE_FROZEN))
/*
 * This is the end of Protocol specific defines.
 */

static int storvsc_ringbuffer_size = (256 * PAGE_SIZE);
static u32 max_outstanding_req_per_channel;

static int storvsc_vcpus_per_sub_channel = 4;

module_param(storvsc_ringbuffer_size, int, S_IRUGO);
MODULE_PARM_DESC(storvsc_ringbuffer_size, "Ring buffer size (bytes)");

module_param(storvsc_vcpus_per_sub_channel, int, S_IRUGO);
MODULE_PARM_DESC(vcpus_per_sub_channel, "Ratio of VCPUs to subchannels");
/*
 * Timeout in seconds for all devices managed by this driver.
 */
static int storvsc_timeout = 180;

static int msft_blist_flags = BLIST_TRY_VPD_PAGES;


static void storvsc_on_channel_callback(void *context);

#define STORVSC_MAX_LUNS_PER_TARGET                     255
#define STORVSC_MAX_TARGETS                             2
#define STORVSC_MAX_CHANNELS                            8

#define STORVSC_FC_MAX_LUNS_PER_TARGET                  255
#define STORVSC_FC_MAX_TARGETS                          128
#define STORVSC_FC_MAX_CHANNELS                         8

#define STORVSC_IDE_MAX_LUNS_PER_TARGET                 64
#define STORVSC_IDE_MAX_TARGETS                         1
#define STORVSC_IDE_MAX_CHANNELS                        1

struct storvsc_cmd_request {
        struct scsi_cmnd *cmd;

        struct hv_device *device;

        /* Synchronize the request/response if needed */
        struct completion wait_event;

        struct vmbus_channel_packet_multipage_buffer mpb;
        struct vmbus_packet_mpb_array *payload;
        u32 payload_sz;

        struct vstor_packet vstor_packet;
};


/* A storvsc device is a device object that contains a vmbus channel */
struct storvsc_device {
        struct hv_device *device;

        bool     destroy;
        bool     drain_notify;
        bool     open_sub_channel;
        atomic_t num_outstanding_req;
        struct Scsi_Host *host;

        wait_queue_head_t waiting_to_drain;

        /*
         * Each unique Port/Path/Target represents 1 channel ie scsi
         * controller. In reality, the pathid, targetid is always 0
         * and the port is set by us
         */
        unsigned int port_number;
        unsigned char path_id;
        unsigned char target_id;

        /*
         * Max I/O, the device can support.
         */
        u32   max_transfer_bytes;
        /* Used for vsc/vsp channel reset process */
        struct storvsc_cmd_request init_request;
        struct storvsc_cmd_request reset_request;
};

struct hv_host_device {
        struct hv_device *dev;
        unsigned int port;
        unsigned char path;
        unsigned char target;
};

struct storvsc_scan_work {
        struct work_struct work;
        struct Scsi_Host *host;
        uint lun;
};

static void storvsc_device_scan(struct work_struct *work)
{
        struct storvsc_scan_work *wrk;
        uint lun;
        struct scsi_device *sdev;

        wrk = container_of(work, struct storvsc_scan_work, work);
        lun = wrk->lun;

        sdev = scsi_device_lookup(wrk->host, 0, 0, lun);
        if (!sdev)
                goto done;
        scsi_rescan_device(&sdev->sdev_gendev);
        scsi_device_put(sdev);

done:
        kfree(wrk);
}

static void storvsc_host_scan(struct work_struct *work)
{
        struct storvsc_scan_work *wrk;
        struct Scsi_Host *host;
        struct scsi_device *sdev;

        wrk = container_of(work, struct storvsc_scan_work, work);
        host = wrk->host;

        /*
         * Before scanning the host, first check to see if any of the
         * currrently known devices have been hot removed. We issue a
         * "unit ready" command against all currently known devices.
         * This I/O will result in an error for devices that have been
         * removed. As part of handling the I/O error, we remove the device.
         *
         * When a LUN is added or removed, the host sends us a signal to
         * scan the host. Thus we are forced to discover the LUNs that
         * may have been removed this way.
         */
        mutex_lock(&host->scan_mutex);
        shost_for_each_device(sdev, host)
                scsi_test_unit_ready(sdev, 1, 1, NULL);
        mutex_unlock(&host->scan_mutex);
        /*
         * Now scan the host to discover LUNs that may have been added.
         */
        scsi_scan_host(host);

        kfree(wrk);
}

static void storvsc_remove_lun(struct work_struct *work)
{
        struct storvsc_scan_work *wrk;
        struct scsi_device *sdev;

        wrk = container_of(work, struct storvsc_scan_work, work);
        if (!scsi_host_get(wrk->host))
                goto done;

        sdev = scsi_device_lookup(wrk->host, 0, 0, wrk->lun);

        if (sdev) {
                scsi_remove_device(sdev);
                scsi_device_put(sdev);
        }
        scsi_host_put(wrk->host);

done:
        kfree(wrk);
}


/*
 * We can get incoming messages from the host that are not in response to
 * messages that we have sent out. An example of this would be messages
 * received by the guest to notify dynamic addition/removal of LUNs. To
 * deal with potential race conditions where the driver may be in the
 * midst of being unloaded when we might receive an unsolicited message
 * from the host, we have implemented a mechanism to gurantee sequential
 * consistency:
 *
 * 1) Once the device is marked as being destroyed, we will fail all
 *    outgoing messages.
 * 2) We permit incoming messages when the device is being destroyed,
 *    only to properly account for messages already sent out.
 */

static inline struct storvsc_device *get_out_stor_device(
                                        struct hv_device *device)
{
        struct storvsc_device *stor_device;

        stor_device = hv_get_drvdata(device);

        if (stor_device && stor_device->destroy)
                stor_device = NULL;

        return stor_device;
}


static inline void storvsc_wait_to_drain(struct storvsc_device *dev)
{
        dev->drain_notify = true;
        wait_event(dev->waiting_to_drain,
                   atomic_read(&dev->num_outstanding_req) == 0);
        dev->drain_notify = false;
}

static inline struct storvsc_device *get_in_stor_device(
                                        struct hv_device *device)
{
        struct storvsc_device *stor_device;

        stor_device = hv_get_drvdata(device);

        if (!stor_device)
                goto get_in_err;

        /*
         * If the device is being destroyed; allow incoming
         * traffic only to cleanup outstanding requests.
         */

        if (stor_device->destroy  &&
                (atomic_read(&stor_device->num_outstanding_req) == 0))
                stor_device = NULL;

get_in_err:
        return stor_device;

}

static void handle_sc_creation(struct vmbus_channel *new_sc)
{
        struct hv_device *device = new_sc->primary_channel->device_obj;
        struct storvsc_device *stor_device;
        struct vmstorage_channel_properties props;

        stor_device = get_out_stor_device(device);
        if (!stor_device)
                return;

        if (stor_device->open_sub_channel == false)
                return;

        memset(&props, 0, sizeof(struct vmstorage_channel_properties));

        vmbus_open(new_sc,
                   storvsc_ringbuffer_size,
                   storvsc_ringbuffer_size,
                   (void *)&props,
                   sizeof(struct vmstorage_channel_properties),
                   storvsc_on_channel_callback, new_sc);
}

static void  handle_multichannel_storage(struct hv_device *device, int max_chns)
{
        struct storvsc_device *stor_device;
        int num_cpus = num_online_cpus();
        int num_sc;
        struct storvsc_cmd_request *request;
        struct vstor_packet *vstor_packet;
        int ret, t;

        num_sc = ((max_chns > num_cpus) ? num_cpus : max_chns);
        stor_device = get_out_stor_device(device);
        if (!stor_device)
                return;

        request = &stor_device->init_request;
        vstor_packet = &request->vstor_packet;

        stor_device->open_sub_channel = true;
        /*
         * Establish a handler for dealing with subchannels.
         */
        vmbus_set_sc_create_callback(device->channel, handle_sc_creation);

        /*
         * Check to see if sub-channels have already been created. This
         * can happen when this driver is re-loaded after unloading.
         */

        if (vmbus_are_subchannels_present(device->channel))
                return;

        stor_device->open_sub_channel = false;
        /*
         * Request the host to create sub-channels.
         */
        memset(request, 0, sizeof(struct storvsc_cmd_request));
        init_completion(&request->wait_event);
        vstor_packet->operation = VSTOR_OPERATION_CREATE_SUB_CHANNELS;
        vstor_packet->flags = REQUEST_COMPLETION_FLAG;
        vstor_packet->sub_channel_count = num_sc;

        ret = vmbus_sendpacket(device->channel, vstor_packet,
                               (sizeof(struct vstor_packet) -
                               vmscsi_size_delta),
                               (unsigned long)request,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);

        if (ret != 0)
                return;

        t = wait_for_completion_timeout(&request->wait_event, 10*HZ);
        if (t == 0)
                return;

        if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO ||
            vstor_packet->status != 0)
                return;

        /*
         * Now that we created the sub-channels, invoke the check; this
         * may trigger the callback.
         */
        stor_device->open_sub_channel = true;
        vmbus_are_subchannels_present(device->channel);
}

static int storvsc_channel_init(struct hv_device *device)
{
        struct storvsc_device *stor_device;
        struct storvsc_cmd_request *request;
        struct vstor_packet *vstor_packet;
        int ret, t, i;
        int max_chns;
        bool process_sub_channels = false;

        stor_device = get_out_stor_device(device);
        if (!stor_device)
                return -ENODEV;

        request = &stor_device->init_request;
        vstor_packet = &request->vstor_packet;

        /*
         * Now, initiate the vsc/vsp initialization protocol on the open
         * channel
         */
        memset(request, 0, sizeof(struct storvsc_cmd_request));
        init_completion(&request->wait_event);
        vstor_packet->operation = VSTOR_OPERATION_BEGIN_INITIALIZATION;
        vstor_packet->flags = REQUEST_COMPLETION_FLAG;

        ret = vmbus_sendpacket(device->channel, vstor_packet,
                               (sizeof(struct vstor_packet) -
                               vmscsi_size_delta),
                               (unsigned long)request,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (ret != 0)
                goto cleanup;

        t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
        if (t == 0) {
                ret = -ETIMEDOUT;
                goto cleanup;
        }

        if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO ||
            vstor_packet->status != 0) {
                ret = -EINVAL;
                goto cleanup;
        }


        for (i = 0; i < ARRAY_SIZE(vmstor_protocols); i++) {
                /* reuse the packet for version range supported */
                memset(vstor_packet, 0, sizeof(struct vstor_packet));
                vstor_packet->operation =
                        VSTOR_OPERATION_QUERY_PROTOCOL_VERSION;
                vstor_packet->flags = REQUEST_COMPLETION_FLAG;

                vstor_packet->version.major_minor =
                        vmstor_protocols[i].protocol_version;

                /*
                 * The revision number is only used in Windows; set it to 0.
                 */
                vstor_packet->version.revision = 0;

                ret = vmbus_sendpacket(device->channel, vstor_packet,
                               (sizeof(struct vstor_packet) -
                                vmscsi_size_delta),
                               (unsigned long)request,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
                if (ret != 0)
                        goto cleanup;

                t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
                if (t == 0) {
                        ret = -ETIMEDOUT;
                        goto cleanup;
                }

                if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO) {
                        ret = -EINVAL;
                        goto cleanup;
                }

                if (vstor_packet->status == 0) {
                        vmstor_proto_version =
                                vmstor_protocols[i].protocol_version;

                        sense_buffer_size =
                                vmstor_protocols[i].sense_buffer_size;

                        vmscsi_size_delta =
                                vmstor_protocols[i].vmscsi_size_delta;

                        break;
                }
        }

        if (vstor_packet->status != 0) {
                ret = -EINVAL;
                goto cleanup;
        }


        memset(vstor_packet, 0, sizeof(struct vstor_packet));
        vstor_packet->operation = VSTOR_OPERATION_QUERY_PROPERTIES;
        vstor_packet->flags = REQUEST_COMPLETION_FLAG;

        ret = vmbus_sendpacket(device->channel, vstor_packet,
                               (sizeof(struct vstor_packet) -
                                vmscsi_size_delta),
                               (unsigned long)request,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);

        if (ret != 0)
                goto cleanup;

        t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
        if (t == 0) {
                ret = -ETIMEDOUT;
                goto cleanup;
        }

        if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO ||
            vstor_packet->status != 0) {
                ret = -EINVAL;
                goto cleanup;
        }

        /*
         * Check to see if multi-channel support is there.
         * Hosts that implement protocol version of 5.1 and above
         * support multi-channel.
         */
        max_chns = vstor_packet->storage_channel_properties.max_channel_cnt;
        if (vmstor_proto_version >= VMSTOR_PROTO_VERSION_WIN8) {
                if (vstor_packet->storage_channel_properties.flags &
                    STORAGE_CHANNEL_SUPPORTS_MULTI_CHANNEL)
                        process_sub_channels = true;
        }
        stor_device->max_transfer_bytes =
                vstor_packet->storage_channel_properties.max_transfer_bytes;

        memset(vstor_packet, 0, sizeof(struct vstor_packet));
        vstor_packet->operation = VSTOR_OPERATION_END_INITIALIZATION;
        vstor_packet->flags = REQUEST_COMPLETION_FLAG;

        ret = vmbus_sendpacket(device->channel, vstor_packet,
                               (sizeof(struct vstor_packet) -
                                vmscsi_size_delta),
                               (unsigned long)request,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);

        if (ret != 0)
                goto cleanup;

        t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
        if (t == 0) {
                ret = -ETIMEDOUT;
                goto cleanup;
        }

        if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO ||
            vstor_packet->status != 0) {
                ret = -EINVAL;
                goto cleanup;
        }

        if (process_sub_channels)
                handle_multichannel_storage(device, max_chns);


cleanup:
        return ret;
}

static void storvsc_handle_error(struct vmscsi_request *vm_srb,
                                struct scsi_cmnd *scmnd,
                                struct Scsi_Host *host,
                                u8 asc, u8 ascq)
{
        struct storvsc_scan_work *wrk;
        void (*process_err_fn)(struct work_struct *work);
        bool do_work = false;

        switch (SRB_STATUS(vm_srb->srb_status)) {
        case SRB_STATUS_ERROR:
                /*
                 * If there is an error; offline the device since all
                 * error recovery strategies would have already been
                 * deployed on the host side. However, if the command
                 * were a pass-through command deal with it appropriately.
                 */
                switch (scmnd->cmnd[0]) {
                case ATA_16:
                case ATA_12:
                        set_host_byte(scmnd, DID_PASSTHROUGH);
                        break;
                /*
                 * On Some Windows hosts TEST_UNIT_READY command can return
                 * SRB_STATUS_ERROR, let the upper level code deal with it
                 * based on the sense information.
                 */
                case TEST_UNIT_READY:
                        break;
                default:
                        set_host_byte(scmnd, DID_TARGET_FAILURE);
                }
                break;
        case SRB_STATUS_INVALID_LUN:
                do_work = true;
                process_err_fn = storvsc_remove_lun;
                break;
        case (SRB_STATUS_ABORTED | SRB_STATUS_AUTOSENSE_VALID):
                if ((asc == 0x2a) && (ascq == 0x9)) {
                        do_work = true;
                        process_err_fn = storvsc_device_scan;
                        /*
                         * Retry the I/O that trigerred this.
                         */
                        set_host_byte(scmnd, DID_REQUEUE);
                }
                break;
        }

        if (!do_work)
                return;

        /*
         * We need to schedule work to process this error; schedule it.
         */
        wrk = kmalloc(sizeof(struct storvsc_scan_work), GFP_ATOMIC);
        if (!wrk) {
                set_host_byte(scmnd, DID_TARGET_FAILURE);
                return;
        }

        wrk->host = host;
        wrk->lun = vm_srb->lun;
        INIT_WORK(&wrk->work, process_err_fn);
        schedule_work(&wrk->work);
}


static void storvsc_command_completion(struct storvsc_cmd_request *cmd_request)
{
        struct scsi_cmnd *scmnd = cmd_request->cmd;
        struct hv_host_device *host_dev = shost_priv(scmnd->device->host);
        struct scsi_sense_hdr sense_hdr;
        struct vmscsi_request *vm_srb;
        struct Scsi_Host *host;
        struct storvsc_device *stor_dev;
        struct hv_device *dev = host_dev->dev;
        u32 payload_sz = cmd_request->payload_sz;
        void *payload = cmd_request->payload;

        stor_dev = get_in_stor_device(dev);
        host = stor_dev->host;

        vm_srb = &cmd_request->vstor_packet.vm_srb;

        scmnd->result = vm_srb->scsi_status;

        if (scmnd->result) {
                if (scsi_normalize_sense(scmnd->sense_buffer,
                                SCSI_SENSE_BUFFERSIZE, &sense_hdr))
                        scsi_print_sense_hdr(scmnd->device, "storvsc",
                                             &sense_hdr);
        }

        if (vm_srb->srb_status != SRB_STATUS_SUCCESS)
                storvsc_handle_error(vm_srb, scmnd, host, sense_hdr.asc,
                                         sense_hdr.ascq);

        scsi_set_resid(scmnd,
                cmd_request->payload->range.len -
                vm_srb->data_transfer_length);

        scmnd->scsi_done(scmnd);

        if (payload_sz >
                sizeof(struct vmbus_channel_packet_multipage_buffer))
                kfree(payload);
}

static void storvsc_on_io_completion(struct hv_device *device,
                                  struct vstor_packet *vstor_packet,
                                  struct storvsc_cmd_request *request)
{
        struct storvsc_device *stor_device;
        struct vstor_packet *stor_pkt;

        stor_device = hv_get_drvdata(device);
        stor_pkt = &request->vstor_packet;

        /*
         * The current SCSI handling on the host side does
         * not correctly handle:
         * INQUIRY command with page code parameter set to 0x80
         * MODE_SENSE command with cmd[2] == 0x1c
         *
         * Setup srb and scsi status so this won't be fatal.
         * We do this so we can distinguish truly fatal failues
         * (srb status == 0x4) and off-line the device in that case.
         */

        if ((stor_pkt->vm_srb.cdb[0] == INQUIRY) ||
           (stor_pkt->vm_srb.cdb[0] == MODE_SENSE)) {
                vstor_packet->vm_srb.scsi_status = 0;
                vstor_packet->vm_srb.srb_status = SRB_STATUS_SUCCESS;
        }


        /* Copy over the status...etc */
        stor_pkt->vm_srb.scsi_status = vstor_packet->vm_srb.scsi_status;
        stor_pkt->vm_srb.srb_status = vstor_packet->vm_srb.srb_status;
        stor_pkt->vm_srb.sense_info_length =
        vstor_packet->vm_srb.sense_info_length;


        if ((vstor_packet->vm_srb.scsi_status & 0xFF) == 0x02) {
                /* CHECK_CONDITION */
                if (vstor_packet->vm_srb.srb_status &
                        SRB_STATUS_AUTOSENSE_VALID) {
                        /* autosense data available */

                        memcpy(request->cmd->sense_buffer,
                               vstor_packet->vm_srb.sense_data,
                               vstor_packet->vm_srb.sense_info_length);

                }
        }

        stor_pkt->vm_srb.data_transfer_length =
        vstor_packet->vm_srb.data_transfer_length;

        storvsc_command_completion(request);

        if (atomic_dec_and_test(&stor_device->num_outstanding_req) &&
                stor_device->drain_notify)
                wake_up(&stor_device->waiting_to_drain);


}

static void storvsc_on_receive(struct hv_device *device,
                             struct vstor_packet *vstor_packet,
                             struct storvsc_cmd_request *request)
{
        struct storvsc_scan_work *work;
        struct storvsc_device *stor_device;

        switch (vstor_packet->operation) {
        case VSTOR_OPERATION_COMPLETE_IO:
                storvsc_on_io_completion(device, vstor_packet, request);
                break;

        case VSTOR_OPERATION_REMOVE_DEVICE:
        case VSTOR_OPERATION_ENUMERATE_BUS:
                stor_device = get_in_stor_device(device);
                work = kmalloc(sizeof(struct storvsc_scan_work), GFP_ATOMIC);
                if (!work)
                        return;

                INIT_WORK(&work->work, storvsc_host_scan);
                work->host = stor_device->host;
                schedule_work(&work->work);
                break;

        default:
                break;
        }
}

static void storvsc_on_channel_callback(void *context)
{
        struct vmbus_channel *channel = (struct vmbus_channel *)context;
        struct hv_device *device;
        struct storvsc_device *stor_device;
        u32 bytes_recvd;
        u64 request_id;
        unsigned char packet[ALIGN(sizeof(struct vstor_packet), 8)];
        struct storvsc_cmd_request *request;
        int ret;

        if (channel->primary_channel != NULL)
                device = channel->primary_channel->device_obj;
        else
                device = channel->device_obj;

        stor_device = get_in_stor_device(device);
        if (!stor_device)
                return;

        do {
                ret = vmbus_recvpacket(channel, packet,
                                       ALIGN((sizeof(struct vstor_packet) -
                                             vmscsi_size_delta), 8),
                                       &bytes_recvd, &request_id);
                if (ret == 0 && bytes_recvd > 0) {

                        request = (struct storvsc_cmd_request *)
                                        (unsigned long)request_id;

                        if ((request == &stor_device->init_request) ||
                            (request == &stor_device->reset_request)) {

                                memcpy(&request->vstor_packet, packet,
                                       (sizeof(struct vstor_packet) -
                                        vmscsi_size_delta));
                                complete(&request->wait_event);
                        } else {
                                storvsc_on_receive(device,
                                                (struct vstor_packet *)packet,
                                                request);
                        }
                } else {
                        break;
                }
        } while (1);

        return;
}

static int storvsc_connect_to_vsp(struct hv_device *device, u32 ring_size)
{
        struct vmstorage_channel_properties props;
        int ret;

        memset(&props, 0, sizeof(struct vmstorage_channel_properties));

        ret = vmbus_open(device->channel,
                         ring_size,
                         ring_size,
                         (void *)&props,
                         sizeof(struct vmstorage_channel_properties),
                         storvsc_on_channel_callback, device->channel);

        if (ret != 0)
                return ret;

        ret = storvsc_channel_init(device);

        return ret;
}

static int storvsc_dev_remove(struct hv_device *device)
{
        struct storvsc_device *stor_device;
        unsigned long flags;

        stor_device = hv_get_drvdata(device);

        spin_lock_irqsave(&device->channel->inbound_lock, flags);
        stor_device->destroy = true;
        spin_unlock_irqrestore(&device->channel->inbound_lock, flags);

        /*
         * At this point, all outbound traffic should be disable. We
         * only allow inbound traffic (responses) to proceed so that
         * outstanding requests can be completed.
         */

        storvsc_wait_to_drain(stor_device);

        /*
         * Since we have already drained, we don't need to busy wait
         * as was done in final_release_stor_device()
         * Note that we cannot set the ext pointer to NULL until
         * we have drained - to drain the outgoing packets, we need to
         * allow incoming packets.
         */
        spin_lock_irqsave(&device->channel->inbound_lock, flags);
        hv_set_drvdata(device, NULL);
        spin_unlock_irqrestore(&device->channel->inbound_lock, flags);

        /* Close the channel */
        vmbus_close(device->channel);

        kfree(stor_device);
        return 0;
}

static int storvsc_do_io(struct hv_device *device,
                         struct storvsc_cmd_request *request)
{
        struct storvsc_device *stor_device;
        struct vstor_packet *vstor_packet;
        struct vmbus_channel *outgoing_channel;
        int ret = 0;

        vstor_packet = &request->vstor_packet;
        stor_device = get_out_stor_device(device);

        if (!stor_device)
                return -ENODEV;


        request->device  = device;
        /*
         * Select an an appropriate channel to send the request out.
         */

        outgoing_channel = vmbus_get_outgoing_channel(device->channel);


        vstor_packet->flags |= REQUEST_COMPLETION_FLAG;

        vstor_packet->vm_srb.length = (sizeof(struct vmscsi_request) -
                                        vmscsi_size_delta);


        vstor_packet->vm_srb.sense_info_length = sense_buffer_size;


        vstor_packet->vm_srb.data_transfer_length =
        request->payload->range.len;

        vstor_packet->operation = VSTOR_OPERATION_EXECUTE_SRB;

        if (request->payload->range.len) {

                ret = vmbus_sendpacket_mpb_desc(outgoing_channel,
                                request->payload, request->payload_sz,
                                vstor_packet,
                                (sizeof(struct vstor_packet) -
                                vmscsi_size_delta),
                                (unsigned long)request);
        } else {
                ret = vmbus_sendpacket(outgoing_channel, vstor_packet,
                               (sizeof(struct vstor_packet) -
                                vmscsi_size_delta),
                               (unsigned long)request,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        }

        if (ret != 0)
                return ret;

        atomic_inc(&stor_device->num_outstanding_req);

        return ret;
}

static int storvsc_device_configure(struct scsi_device *sdevice)
{

        blk_queue_max_segment_size(sdevice->request_queue, PAGE_SIZE);

        blk_queue_bounce_limit(sdevice->request_queue, BLK_BOUNCE_ANY);

        blk_queue_rq_timeout(sdevice->request_queue, (storvsc_timeout * HZ));

        /* Ensure there are no gaps in presented sgls */
        blk_queue_virt_boundary(sdevice->request_queue, PAGE_SIZE - 1);

        sdevice->no_write_same = 1;

        /*
         * Add blist flags to permit the reading of the VPD pages even when
         * the target may claim SPC-2 compliance. MSFT targets currently
         * claim SPC-2 compliance while they implement post SPC-2 features.
         * With this patch we can correctly handle WRITE_SAME_16 issues.
         */
        sdevice->sdev_bflags |= msft_blist_flags;

        /*
         * If the host is WIN8 or WIN8 R2, claim conformance to SPC-3
         * if the device is a MSFT virtual device.  If the host is
         * WIN10 or newer, allow write_same.
         */
        if (!strncmp(sdevice->vendor, "Msft", 4)) {
                switch (vmstor_proto_version) {
                case VMSTOR_PROTO_VERSION_WIN8:
                case VMSTOR_PROTO_VERSION_WIN8_1:
                        sdevice->scsi_level = SCSI_SPC_3;
                        break;
                }

                if (vmstor_proto_version >= VMSTOR_PROTO_VERSION_WIN10)
                        sdevice->no_write_same = 0;
        }

        return 0;
}

static int storvsc_get_chs(struct scsi_device *sdev, struct block_device * bdev,
                           sector_t capacity, int *info)
{
        sector_t nsect = capacity;
        sector_t cylinders = nsect;
        int heads, sectors_pt;

        /*
         * We are making up these values; let us keep it simple.
         */
        heads = 0xff;
        sectors_pt = 0x3f;      /* Sectors per track */
        sector_div(cylinders, heads * sectors_pt);
        if ((sector_t)(cylinders + 1) * heads * sectors_pt < nsect)
                cylinders = 0xffff;

        info[0] = heads;
        info[1] = sectors_pt;
        info[2] = (int)cylinders;

        return 0;
}

static int storvsc_host_reset_handler(struct scsi_cmnd *scmnd)
{
        struct hv_host_device *host_dev = shost_priv(scmnd->device->host);
        struct hv_device *device = host_dev->dev;

        struct storvsc_device *stor_device;
        struct storvsc_cmd_request *request;
        struct vstor_packet *vstor_packet;
        int ret, t;


        stor_device = get_out_stor_device(device);
        if (!stor_device)
                return FAILED;

        request = &stor_device->reset_request;
        vstor_packet = &request->vstor_packet;

        init_completion(&request->wait_event);

        vstor_packet->operation = VSTOR_OPERATION_RESET_BUS;
        vstor_packet->flags = REQUEST_COMPLETION_FLAG;
        vstor_packet->vm_srb.path_id = stor_device->path_id;

        ret = vmbus_sendpacket(device->channel, vstor_packet,
                               (sizeof(struct vstor_packet) -
                                vmscsi_size_delta),
                               (unsigned long)&stor_device->reset_request,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (ret != 0)
                return FAILED;

        t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
        if (t == 0)
                return TIMEOUT_ERROR;


        /*
         * At this point, all outstanding requests in the adapter
         * should have been flushed out and return to us
         * There is a potential race here where the host may be in
         * the process of responding when we return from here.
         * Just wait for all in-transit packets to be accounted for
         * before we return from here.
         */
        storvsc_wait_to_drain(stor_device);

        return SUCCESS;
}

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

static bool storvsc_scsi_cmd_ok(struct scsi_cmnd *scmnd)
{
        bool allowed = true;
        u8 scsi_op = scmnd->cmnd[0];

        switch (scsi_op) {
        /* the host does not handle WRITE_SAME, log accident usage */
        case WRITE_SAME:
        /*
         * smartd sends this command and the host does not handle
         * this. So, don't send it.
         */
        case SET_WINDOW:
                scmnd->result = ILLEGAL_REQUEST << 16;
                allowed = false;
                break;
        default:
                break;
        }
        return allowed;
}

static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
{
        int ret;
        struct hv_host_device *host_dev = shost_priv(host);
        struct hv_device *dev = host_dev->dev;
        struct storvsc_cmd_request *cmd_request = scsi_cmd_priv(scmnd);
        int i;
        struct scatterlist *sgl;
        unsigned int sg_count = 0;
        struct vmscsi_request *vm_srb;
        struct scatterlist *cur_sgl;
        struct vmbus_packet_mpb_array  *payload;
        u32 payload_sz;
        u32 length;

        if (vmstor_proto_version <= VMSTOR_PROTO_VERSION_WIN8) {
                /*
                 * On legacy hosts filter unimplemented commands.
                 * Future hosts are expected to correctly handle
                 * unsupported commands. Furthermore, it is
                 * possible that some of the currently
                 * unsupported commands maybe supported in
                 * future versions of the host.
                 */
                if (!storvsc_scsi_cmd_ok(scmnd)) {
                        scmnd->scsi_done(scmnd);
                        return 0;
                }
        }

        /* Setup the cmd request */
        cmd_request->cmd = scmnd;

        vm_srb = &cmd_request->vstor_packet.vm_srb;
        vm_srb->win8_extension.time_out_value = 60;

        vm_srb->win8_extension.srb_flags |=
                SRB_FLAGS_DISABLE_SYNCH_TRANSFER;

        /* Build the SRB */
        switch (scmnd->sc_data_direction) {
        case DMA_TO_DEVICE:
                vm_srb->data_in = WRITE_TYPE;
                vm_srb->win8_extension.srb_flags |= SRB_FLAGS_DATA_OUT;
                break;
        case DMA_FROM_DEVICE:
                vm_srb->data_in = READ_TYPE;
                vm_srb->win8_extension.srb_flags |= SRB_FLAGS_DATA_IN;
                break;
        case DMA_NONE:
                vm_srb->data_in = UNKNOWN_TYPE;
                vm_srb->win8_extension.srb_flags |= SRB_FLAGS_NO_DATA_TRANSFER;
                break;
        default:
                /*
                 * This is DMA_BIDIRECTIONAL or something else we are never
                 * supposed to see here.
                 */
                WARN(1, "Unexpected data direction: %d\n",
                     scmnd->sc_data_direction);
                return -EINVAL;
        }


        vm_srb->port_number = host_dev->port;
        vm_srb->path_id = scmnd->device->channel;
        vm_srb->target_id = scmnd->device->id;
        vm_srb->lun = scmnd->device->lun;

        vm_srb->cdb_length = scmnd->cmd_len;

        memcpy(vm_srb->cdb, scmnd->cmnd, vm_srb->cdb_length);

        sgl = (struct scatterlist *)scsi_sglist(scmnd);
        sg_count = scsi_sg_count(scmnd);

        length = scsi_bufflen(scmnd);
        payload = (struct vmbus_packet_mpb_array *)&cmd_request->mpb;
        payload_sz = sizeof(cmd_request->mpb);

        if (sg_count) {
                if (sg_count > MAX_PAGE_BUFFER_COUNT) {

                        payload_sz = (sg_count * sizeof(void *) +
                                      sizeof(struct vmbus_packet_mpb_array));
                        payload = kmalloc(payload_sz, GFP_ATOMIC);
                        if (!payload)
                                return SCSI_MLQUEUE_DEVICE_BUSY;
                }

                payload->range.len = length;
                payload->range.offset = sgl[0].offset;

                cur_sgl = sgl;
                for (i = 0; i < sg_count; i++) {
                        payload->range.pfn_array[i] =
                                page_to_pfn(sg_page((cur_sgl)));
                        cur_sgl = sg_next(cur_sgl);
                }

        } else if (scsi_sglist(scmnd)) {
                payload->range.len = length;
                payload->range.offset =
                        virt_to_phys(scsi_sglist(scmnd)) & (PAGE_SIZE-1);
                payload->range.pfn_array[0] =
                        virt_to_phys(scsi_sglist(scmnd)) >> PAGE_SHIFT;
        }

        cmd_request->payload = payload;
        cmd_request->payload_sz = payload_sz;

        /* Invokes the vsc to start an IO */
        ret = storvsc_do_io(dev, cmd_request);

        if (ret == -EAGAIN) {
                /* no more space */
                return SCSI_MLQUEUE_DEVICE_BUSY;
        }

        return 0;
}

static struct scsi_host_template scsi_driver = {
        .module =               THIS_MODULE,
        .name =                 "storvsc_host_t",
        .cmd_size =             sizeof(struct storvsc_cmd_request),
        .bios_param =           storvsc_get_chs,
        .queuecommand =         storvsc_queuecommand,
        .eh_host_reset_handler =        storvsc_host_reset_handler,
        .proc_name =            "storvsc_host",
        .eh_timed_out =         storvsc_eh_timed_out,
        .slave_configure =      storvsc_device_configure,
        .cmd_per_lun =          255,
        .this_id =              -1,
        .use_clustering =       ENABLE_CLUSTERING,
        /* Make sure we dont get a sg segment crosses a page boundary */
        .dma_boundary =         PAGE_SIZE-1,
        .no_write_same =        1,
};

enum {
        SCSI_GUID,
        IDE_GUID,
        SFC_GUID,
};

static const struct hv_vmbus_device_id id_table[] = {
        /* SCSI guid */
        { HV_SCSI_GUID,
          .driver_data = SCSI_GUID
        },
        /* IDE guid */
        { HV_IDE_GUID,
          .driver_data = IDE_GUID
        },
        /* Fibre Channel GUID */
        {
          HV_SYNTHFC_GUID,
          .driver_data = SFC_GUID
        },
        { },
};

MODULE_DEVICE_TABLE(vmbus, id_table);

static int storvsc_probe(struct hv_device *device,
                        const struct hv_vmbus_device_id *dev_id)
{
        int ret;
        int num_cpus = num_online_cpus();
        struct Scsi_Host *host;
        struct hv_host_device *host_dev;
        bool dev_is_ide = ((dev_id->driver_data == IDE_GUID) ? true : false);
        int target = 0;
        struct storvsc_device *stor_device;
        int max_luns_per_target;
        int max_targets;
        int max_channels;
        int max_sub_channels = 0;

        /*
         * Based on the windows host we are running on,
         * set state to properly communicate with the host.
         */

        if (vmbus_proto_version < VERSION_WIN8) {
                max_luns_per_target = STORVSC_IDE_MAX_LUNS_PER_TARGET;
                max_targets = STORVSC_IDE_MAX_TARGETS;
                max_channels = STORVSC_IDE_MAX_CHANNELS;
        } else {
                max_luns_per_target = STORVSC_MAX_LUNS_PER_TARGET;
                max_targets = STORVSC_MAX_TARGETS;
                max_channels = STORVSC_MAX_CHANNELS;
                /*
                 * On Windows8 and above, we support sub-channels for storage.
                 * The number of sub-channels offerred is based on the number of
                 * VCPUs in the guest.
                 */
                max_sub_channels = (num_cpus / storvsc_vcpus_per_sub_channel);
        }

        scsi_driver.can_queue = (max_outstanding_req_per_channel *
                                 (max_sub_channels + 1));

        host = scsi_host_alloc(&scsi_driver,
                               sizeof(struct hv_host_device));
        if (!host)
                return -ENOMEM;

        host_dev = shost_priv(host);
        memset(host_dev, 0, sizeof(struct hv_host_device));

        host_dev->port = host->host_no;
        host_dev->dev = device;


        stor_device = kzalloc(sizeof(struct storvsc_device), GFP_KERNEL);
        if (!stor_device) {
                ret = -ENOMEM;
                goto err_out0;
        }

        stor_device->destroy = false;
        stor_device->open_sub_channel = false;
        init_waitqueue_head(&stor_device->waiting_to_drain);
        stor_device->device = device;
        stor_device->host = host;
        hv_set_drvdata(device, stor_device);

        stor_device->port_number = host->host_no;
        ret = storvsc_connect_to_vsp(device, storvsc_ringbuffer_size);
        if (ret)
                goto err_out1;

        host_dev->path = stor_device->path_id;
        host_dev->target = stor_device->target_id;

        switch (dev_id->driver_data) {
        case SFC_GUID:
                host->max_lun = STORVSC_FC_MAX_LUNS_PER_TARGET;
                host->max_id = STORVSC_FC_MAX_TARGETS;
                host->max_channel = STORVSC_FC_MAX_CHANNELS - 1;
                break;

        case SCSI_GUID:
                host->max_lun = max_luns_per_target;
                host->max_id = max_targets;
                host->max_channel = max_channels - 1;
                break;

        default:
                host->max_lun = STORVSC_IDE_MAX_LUNS_PER_TARGET;
                host->max_id = STORVSC_IDE_MAX_TARGETS;
                host->max_channel = STORVSC_IDE_MAX_CHANNELS - 1;
                break;
        }
        /* max cmd length */
        host->max_cmd_len = STORVSC_MAX_CMD_LEN;

        /*
         * set the table size based on the info we got
         * from the host.
         */
        host->sg_tablesize = (stor_device->max_transfer_bytes >> PAGE_SHIFT);

        /* Register the HBA and start the scsi bus scan */
        ret = scsi_add_host(host, &device->device);
        if (ret != 0)
                goto err_out2;

        if (!dev_is_ide) {
                scsi_scan_host(host);
        } else {
                target = (device->dev_instance.b[5] << 8 |
                         device->dev_instance.b[4]);
                ret = scsi_add_device(host, 0, target, 0);
                if (ret) {
                        scsi_remove_host(host);
                        goto err_out2;
                }
        }
        return 0;

err_out2:
        /*
         * Once we have connected with the host, we would need to
         * to invoke storvsc_dev_remove() to rollback this state and
         * this call also frees up the stor_device; hence the jump around
         * err_out1 label.
         */
        storvsc_dev_remove(device);
        goto err_out0;

err_out1:
        kfree(stor_device);

err_out0:
        scsi_host_put(host);
        return ret;
}

static int storvsc_remove(struct hv_device *dev)
{
        struct storvsc_device *stor_device = hv_get_drvdata(dev);
        struct Scsi_Host *host = stor_device->host;

        scsi_remove_host(host);
        storvsc_dev_remove(dev);
        scsi_host_put(host);

        return 0;
}

static struct hv_driver storvsc_drv = {
        .name = KBUILD_MODNAME,
        .id_table = id_table,
        .probe = storvsc_probe,
        .remove = storvsc_remove,
};

static int __init storvsc_drv_init(void)
{

        /*
         * Divide the ring buffer data size (which is 1 page less
         * than the ring buffer size since that page is reserved for
         * the ring buffer indices) by the max request size (which is
         * vmbus_channel_packet_multipage_buffer + struct vstor_packet + u64)
         */
        max_outstanding_req_per_channel =
                ((storvsc_ringbuffer_size - PAGE_SIZE) /
                ALIGN(MAX_MULTIPAGE_BUFFER_PACKET +
                sizeof(struct vstor_packet) + sizeof(u64) -
                vmscsi_size_delta,
                sizeof(u64)));

        return vmbus_driver_register(&storvsc_drv);
}

static void __exit storvsc_drv_exit(void)
{
        vmbus_driver_unregister(&storvsc_drv);
}

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Microsoft Hyper-V virtual storage driver");
module_init(storvsc_drv_init);
module_exit(storvsc_drv_exit);