Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2227 insertions, 0 deletions

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
new file mode 100644
index 000000000..c2d981d5a
--- /dev/null
+++ b/drivers/scsi/storvsc_drv.c
@@ -0,0 +1,2227 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2009, Microsoft Corporation.
+ *
+ * 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 <linux/dma-mapping.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>
+#include <scsi/scsi_transport_fc.h>
+#include <scsi/scsi_transport.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)
+
+/* channel callback timeout in ms */
+#define CALLBACK_TIMEOUT               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 {
+	u8	primary_active;
+	u8	reserved1[3];
+	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
+
+#define SP_UNTAGGED			((unsigned char) ~0)
+#define SRB_SIMPLE_TAG_REQUEST		0x20
+
+/*
+ * 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
+
+/* Sense buffer size is the same for all versions since Windows 8 */
+#define STORVSC_SENSE_BUFFER_SIZE		0x14
+#define STORVSC_MAX_BUF_LEN_WITH_PADDING	0x14
+
+/*
+ * 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;
+
+#define STORVSC_LOGGING_NONE	0
+#define STORVSC_LOGGING_ERROR	1
+#define STORVSC_LOGGING_WARN	2
+
+static int logging_level = STORVSC_LOGGING_ERROR;
+module_param(logging_level, int, S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(logging_level,
+	"Logging level, 0 - None, 1 - Error (default), 2 - Warning.");
+
+static inline bool do_logging(int level)
+{
+	return logging_level >= level;
+}
+
+#define storvsc_log(dev, level, fmt, ...)			\
+do {								\
+	if (do_logging(level))					\
+		dev_warn(&(dev)->device, fmt, ##__VA_ARGS__);	\
+} while (0)
+
+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.
+	 */
+	u16 reserve;
+	u8  queue_tag;
+	u8  queue_action;
+	u32 srb_flags;
+	u32 time_out_value;
+	u32 queue_sort_ey;
+
+} __attribute((packed));
+
+/*
+ * The list of windows version in order of preference.
+ */
+
+static const int protocol_version[] = {
+		VMSTOR_PROTO_VERSION_WIN10,
+		VMSTOR_PROTO_VERSION_WIN8_1,
+		VMSTOR_PROTO_VERSION_WIN8,
+};
+
+
+/*
+ * This structure is sent during the initialization 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. In the 8-bit field, the two high order bits
+ * are flags, while the remaining 6 bits are an integer status code.  The
+ * definitions here include only the subset of the integer status codes that
+ * are tested for in this driver.
+ */
+#define SRB_STATUS_AUTOSENSE_VALID	0x80
+#define SRB_STATUS_QUEUE_FROZEN		0x40
+
+/* SRB status integer codes */
+#define SRB_STATUS_SUCCESS		0x01
+#define SRB_STATUS_ABORTED		0x02
+#define SRB_STATUS_ERROR		0x04
+#define SRB_STATUS_INVALID_REQUEST	0x06
+#define SRB_STATUS_DATA_OVERRUN		0x12
+#define SRB_STATUS_INVALID_LUN		0x20
+
+#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 = (128 * 1024);
+static u32 max_outstanding_req_per_channel;
+static int storvsc_change_queue_depth(struct scsi_device *sdev, int queue_depth);
+
+static int storvsc_vcpus_per_sub_channel = 4;
+static unsigned int storvsc_max_hw_queues;
+
+module_param(storvsc_ringbuffer_size, int, S_IRUGO);
+MODULE_PARM_DESC(storvsc_ringbuffer_size, "Ring buffer size (bytes)");
+
+module_param(storvsc_max_hw_queues, uint, 0644);
+MODULE_PARM_DESC(storvsc_max_hw_queues, "Maximum number of hardware queues");
+
+module_param(storvsc_vcpus_per_sub_channel, int, S_IRUGO);
+MODULE_PARM_DESC(storvsc_vcpus_per_sub_channel, "Ratio of VCPUs to subchannels");
+
+static int ring_avail_percent_lowater = 10;
+module_param(ring_avail_percent_lowater, int, S_IRUGO);
+MODULE_PARM_DESC(ring_avail_percent_lowater,
+		"Select a channel if available ring size > this in percent");
+
+/*
+ * Timeout in seconds for all devices managed by this driver.
+ */
+static int storvsc_timeout = 180;
+
+#if IS_ENABLED(CONFIG_SCSI_FC_ATTRS)
+static struct scsi_transport_template *fc_transport_template;
+#endif
+
+static struct scsi_host_template scsi_driver;
+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_FC_MAX_XFER_SIZE			((u32)(512 * 1024))
+
+#define STORVSC_IDE_MAX_LUNS_PER_TARGET			64
+#define STORVSC_IDE_MAX_TARGETS				1
+#define STORVSC_IDE_MAX_CHANNELS			1
+
+/*
+ * Upper bound on the size of a storvsc packet.
+ */
+#define STORVSC_MAX_PKT_SIZE (sizeof(struct vmpacket_descriptor) +\
+			      sizeof(struct vstor_packet))
+
+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;
+	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;
+	/*
+	 * Number of sub-channels we will open.
+	 */
+	u16 num_sc;
+	struct vmbus_channel **stor_chns;
+	/*
+	 * Mask of CPUs bound to subchannels.
+	 */
+	struct cpumask alloced_cpus;
+	/*
+	 * Serializes modifications of stor_chns[] from storvsc_do_io()
+	 * and storvsc_change_target_cpu().
+	 */
+	spinlock_t lock;
+	/* Used for vsc/vsp channel reset process */
+	struct storvsc_cmd_request init_request;
+	struct storvsc_cmd_request reset_request;
+	/*
+	 * Currently active port and node names for FC devices.
+	 */
+	u64 node_name;
+	u64 port_name;
+#if IS_ENABLED(CONFIG_SCSI_FC_ATTRS)
+	struct fc_rport *rport;
+#endif
+};
+
+struct hv_host_device {
+	struct hv_device *dev;
+	unsigned int port;
+	unsigned char path;
+	unsigned char target;
+	struct workqueue_struct *handle_error_wq;
+	struct work_struct host_scan_work;
+	struct Scsi_Host *host;
+};
+
+struct storvsc_scan_work {
+	struct work_struct work;
+	struct Scsi_Host *host;
+	u8 lun;
+	u8 tgt_id;
+};
+
+static void storvsc_device_scan(struct work_struct *work)
+{
+	struct storvsc_scan_work *wrk;
+	struct scsi_device *sdev;
+
+	wrk = container_of(work, struct storvsc_scan_work, work);
+
+	sdev = scsi_device_lookup(wrk->host, 0, wrk->tgt_id, wrk->lun);
+	if (!sdev)
+		goto done;
+	scsi_rescan_device(sdev);
+	scsi_device_put(sdev);
+
+done:
+	kfree(wrk);
+}
+
+static void storvsc_host_scan(struct work_struct *work)
+{
+	struct Scsi_Host *host;
+	struct scsi_device *sdev;
+	struct hv_host_device *host_device =
+		container_of(work, struct hv_host_device, host_scan_work);
+
+	host = host_device->host;
+	/*
+	 * Before scanning the host, first check to see if any of the
+	 * currently 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);
+}
+
+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, wrk->tgt_id, 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 storvsc_change_target_cpu(struct vmbus_channel *channel, u32 old,
+				      u32 new)
+{
+	struct storvsc_device *stor_device;
+	struct vmbus_channel *cur_chn;
+	bool old_is_alloced = false;
+	struct hv_device *device;
+	unsigned long flags;
+	int cpu;
+
+	device = channel->primary_channel ?
+			channel->primary_channel->device_obj
+				: channel->device_obj;
+	stor_device = get_out_stor_device(device);
+	if (!stor_device)
+		return;
+
+	/* See storvsc_do_io() -> get_og_chn(). */
+	spin_lock_irqsave(&stor_device->lock, flags);
+
+	/*
+	 * Determines if the storvsc device has other channels assigned to
+	 * the "old" CPU to update the alloced_cpus mask and the stor_chns
+	 * array.
+	 */
+	if (device->channel != channel && device->channel->target_cpu == old) {
+		cur_chn = device->channel;
+		old_is_alloced = true;
+		goto old_is_alloced;
+	}
+	list_for_each_entry(cur_chn, &device->channel->sc_list, sc_list) {
+		if (cur_chn == channel)
+			continue;
+		if (cur_chn->target_cpu == old) {
+			old_is_alloced = true;
+			goto old_is_alloced;
+		}
+	}
+
+old_is_alloced:
+	if (old_is_alloced)
+		WRITE_ONCE(stor_device->stor_chns[old], cur_chn);
+	else
+		cpumask_clear_cpu(old, &stor_device->alloced_cpus);
+
+	/* "Flush" the stor_chns array. */
+	for_each_possible_cpu(cpu) {
+		if (stor_device->stor_chns[cpu] && !cpumask_test_cpu(
+					cpu, &stor_device->alloced_cpus))
+			WRITE_ONCE(stor_device->stor_chns[cpu], NULL);
+	}
+
+	WRITE_ONCE(stor_device->stor_chns[new], channel);
+	cpumask_set_cpu(new, &stor_device->alloced_cpus);
+
+	spin_unlock_irqrestore(&stor_device->lock, flags);
+}
+
+static u64 storvsc_next_request_id(struct vmbus_channel *channel, u64 rqst_addr)
+{
+	struct storvsc_cmd_request *request =
+		(struct storvsc_cmd_request *)(unsigned long)rqst_addr;
+
+	if (rqst_addr == VMBUS_RQST_INIT)
+		return VMBUS_RQST_INIT;
+	if (rqst_addr == VMBUS_RQST_RESET)
+		return VMBUS_RQST_RESET;
+
+	/*
+	 * Cannot return an ID of 0, which is reserved for an unsolicited
+	 * message from Hyper-V.
+	 */
+	return (u64)blk_mq_unique_tag(scsi_cmd_to_rq(request->cmd)) + 1;
+}
+
+static void handle_sc_creation(struct vmbus_channel *new_sc)
+{
+	struct hv_device *device = new_sc->primary_channel->device_obj;
+	struct device *dev = &device->device;
+	struct storvsc_device *stor_device;
+	struct vmstorage_channel_properties props;
+	int ret;
+
+	stor_device = get_out_stor_device(device);
+	if (!stor_device)
+		return;
+
+	memset(&props, 0, sizeof(struct vmstorage_channel_properties));
+	new_sc->max_pkt_size = STORVSC_MAX_PKT_SIZE;
+
+	new_sc->next_request_id_callback = storvsc_next_request_id;
+
+	ret = vmbus_open(new_sc,
+			 storvsc_ringbuffer_size,
+			 storvsc_ringbuffer_size,
+			 (void *)&props,
+			 sizeof(struct vmstorage_channel_properties),
+			 storvsc_on_channel_callback, new_sc);
+
+	/* In case vmbus_open() fails, we don't use the sub-channel. */
+	if (ret != 0) {
+		dev_err(dev, "Failed to open sub-channel: err=%d\n", ret);
+		return;
+	}
+
+	new_sc->change_target_cpu_callback = storvsc_change_target_cpu;
+
+	/* Add the sub-channel to the array of available channels. */
+	stor_device->stor_chns[new_sc->target_cpu] = new_sc;
+	cpumask_set_cpu(new_sc->target_cpu, &stor_device->alloced_cpus);
+}
+
+static void  handle_multichannel_storage(struct hv_device *device, int max_chns)
+{
+	struct device *dev = &device->device;
+	struct storvsc_device *stor_device;
+	int num_sc;
+	struct storvsc_cmd_request *request;
+	struct vstor_packet *vstor_packet;
+	int ret, t;
+
+	/*
+	 * If the number of CPUs is artificially restricted, such as
+	 * with maxcpus=1 on the kernel boot line, Hyper-V could offer
+	 * sub-channels >= the number of CPUs. These sub-channels
+	 * should not be created. The primary channel is already created
+	 * and assigned to one CPU, so check against # CPUs - 1.
+	 */
+	num_sc = min((int)(num_online_cpus() - 1), max_chns);
+	if (!num_sc)
+		return;
+
+	stor_device = get_out_stor_device(device);
+	if (!stor_device)
+		return;
+
+	stor_device->num_sc = num_sc;
+	request = &stor_device->init_request;
+	vstor_packet = &request->vstor_packet;
+
+	/*
+	 * Establish a handler for dealing with subchannels.
+	 */
+	vmbus_set_sc_create_callback(device->channel, handle_sc_creation);
+
+	/*
+	 * 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),
+			       VMBUS_RQST_INIT,
+			       VM_PKT_DATA_INBAND,
+			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+
+	if (ret != 0) {
+		dev_err(dev, "Failed to create sub-channel: err=%d\n", ret);
+		return;
+	}
+
+	t = wait_for_completion_timeout(&request->wait_event, 10*HZ);
+	if (t == 0) {
+		dev_err(dev, "Failed to create sub-channel: timed out\n");
+		return;
+	}
+
+	if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO ||
+	    vstor_packet->status != 0) {
+		dev_err(dev, "Failed to create sub-channel: op=%d, sts=%d\n",
+			vstor_packet->operation, vstor_packet->status);
+		return;
+	}
+
+	/*
+	 * We need to do nothing here, because vmbus_process_offer()
+	 * invokes channel->sc_creation_callback, which will open and use
+	 * the sub-channel(s).
+	 */
+}
+
+static void cache_wwn(struct storvsc_device *stor_device,
+		      struct vstor_packet *vstor_packet)
+{
+	/*
+	 * Cache the currently active port and node ww names.
+	 */
+	if (vstor_packet->wwn_packet.primary_active) {
+		stor_device->node_name =
+			wwn_to_u64(vstor_packet->wwn_packet.primary_node_wwn);
+		stor_device->port_name =
+			wwn_to_u64(vstor_packet->wwn_packet.primary_port_wwn);
+	} else {
+		stor_device->node_name =
+			wwn_to_u64(vstor_packet->wwn_packet.secondary_node_wwn);
+		stor_device->port_name =
+			wwn_to_u64(vstor_packet->wwn_packet.secondary_port_wwn);
+	}
+}
+
+
+static int storvsc_execute_vstor_op(struct hv_device *device,
+				    struct storvsc_cmd_request *request,
+				    bool status_check)
+{
+	struct storvsc_device *stor_device;
+	struct vstor_packet *vstor_packet;
+	int ret, t;
+
+	stor_device = get_out_stor_device(device);
+	if (!stor_device)
+		return -ENODEV;
+
+	vstor_packet = &request->vstor_packet;
+
+	init_completion(&request->wait_event);
+	vstor_packet->flags = REQUEST_COMPLETION_FLAG;
+
+	ret = vmbus_sendpacket(device->channel, vstor_packet,
+			       sizeof(struct vstor_packet),
+			       VMBUS_RQST_INIT,
+			       VM_PKT_DATA_INBAND,
+			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+	if (ret != 0)
+		return ret;
+
+	t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
+	if (t == 0)
+		return -ETIMEDOUT;
+
+	if (!status_check)
+		return ret;
+
+	if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO ||
+	    vstor_packet->status != 0)
+		return -EINVAL;
+
+	return ret;
+}
+
+static int storvsc_channel_init(struct hv_device *device, bool is_fc)
+{
+	struct storvsc_device *stor_device;
+	struct storvsc_cmd_request *request;
+	struct vstor_packet *vstor_packet;
+	int ret, 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));
+	vstor_packet->operation = VSTOR_OPERATION_BEGIN_INITIALIZATION;
+	ret = storvsc_execute_vstor_op(device, request, true);
+	if (ret)
+		return ret;
+	/*
+	 * Query host supported protocol version.
+	 */
+
+	for (i = 0; i < ARRAY_SIZE(protocol_version); 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->version.major_minor = protocol_version[i];
+
+		/*
+		 * The revision number is only used in Windows; set it to 0.
+		 */
+		vstor_packet->version.revision = 0;
+		ret = storvsc_execute_vstor_op(device, request, false);
+		if (ret != 0)
+			return ret;
+
+		if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO)
+			return -EINVAL;
+
+		if (vstor_packet->status == 0) {
+			vmstor_proto_version = protocol_version[i];
+
+			break;
+		}
+	}
+
+	if (vstor_packet->status != 0) {
+		dev_err(&device->device, "Obsolete Hyper-V version\n");
+		return -EINVAL;
+	}
+
+
+	memset(vstor_packet, 0, sizeof(struct vstor_packet));
+	vstor_packet->operation = VSTOR_OPERATION_QUERY_PROPERTIES;
+	ret = storvsc_execute_vstor_op(device, request, true);
+	if (ret != 0)
+		return ret;
+
+	/*
+	 * 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;
+
+	/*
+	 * Allocate state to manage the sub-channels.
+	 * We allocate an array based on the numbers of possible CPUs
+	 * (Hyper-V does not support cpu online/offline).
+	 * This Array will be sparseley populated with unique
+	 * channels - primary + sub-channels.
+	 * We will however populate all the slots to evenly distribute
+	 * the load.
+	 */
+	stor_device->stor_chns = kcalloc(num_possible_cpus(), sizeof(void *),
+					 GFP_KERNEL);
+	if (stor_device->stor_chns == NULL)
+		return -ENOMEM;
+
+	device->channel->change_target_cpu_callback = storvsc_change_target_cpu;
+
+	stor_device->stor_chns[device->channel->target_cpu] = device->channel;
+	cpumask_set_cpu(device->channel->target_cpu,
+			&stor_device->alloced_cpus);
+
+	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;
+
+	if (!is_fc)
+		goto done;
+
+	/*
+	 * For FC devices retrieve FC HBA data.
+	 */
+	memset(vstor_packet, 0, sizeof(struct vstor_packet));
+	vstor_packet->operation = VSTOR_OPERATION_FCHBA_DATA;
+	ret = storvsc_execute_vstor_op(device, request, true);
+	if (ret != 0)
+		return ret;
+
+	/*
+	 * Cache the currently active port and node ww names.
+	 */
+	cache_wwn(stor_device, vstor_packet);
+
+done:
+
+	memset(vstor_packet, 0, sizeof(struct vstor_packet));
+	vstor_packet->operation = VSTOR_OPERATION_END_INITIALIZATION;
+	ret = storvsc_execute_vstor_op(device, request, true);
+	if (ret != 0)
+		return ret;
+
+	if (process_sub_channels)
+		handle_multichannel_storage(device, max_chns);
+
+	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);
+	struct hv_host_device *host_dev = shost_priv(host);
+
+	switch (SRB_STATUS(vm_srb->srb_status)) {
+	case SRB_STATUS_ERROR:
+	case SRB_STATUS_ABORTED:
+	case SRB_STATUS_INVALID_REQUEST:
+		if (vm_srb->srb_status & SRB_STATUS_AUTOSENSE_VALID) {
+			/* Check for capacity change */
+			if ((asc == 0x2a) && (ascq == 0x9)) {
+				process_err_fn = storvsc_device_scan;
+				/* Retry the I/O that triggered this. */
+				set_host_byte(scmnd, DID_REQUEUE);
+				goto do_work;
+			}
+
+			/*
+			 * Check for "Operating parameters have changed"
+			 * due to Hyper-V changing the VHD/VHDX BlockSize
+			 * when adding/removing a differencing disk. This
+			 * causes discard_granularity to change, so do a
+			 * rescan to pick up the new granularity. We don't
+			 * want scsi_report_sense() to output a message
+			 * that a sysadmin wouldn't know what to do with.
+			 */
+			if ((asc == 0x3f) && (ascq != 0x03) &&
+					(ascq != 0x0e)) {
+				process_err_fn = storvsc_device_scan;
+				set_host_byte(scmnd, DID_REQUEUE);
+				goto do_work;
+			}
+
+			/*
+			 * Otherwise, let upper layer deal with the
+			 * error when sense message is present
+			 */
+			return;
+		}
+
+		/*
+		 * 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 Hyper-V 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_ERROR);
+		}
+		return;
+
+	case SRB_STATUS_INVALID_LUN:
+		set_host_byte(scmnd, DID_NO_CONNECT);
+		process_err_fn = storvsc_remove_lun;
+		goto do_work;
+
+	}
+	return;
+
+do_work:
+	/*
+	 * 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_BAD_TARGET);
+		return;
+	}
+
+	wrk->host = host;
+	wrk->lun = vm_srb->lun;
+	wrk->tgt_id = vm_srb->target_id;
+	INIT_WORK(&wrk->work, process_err_fn);
+	queue_work(host_dev->handle_error_wq, &wrk->work);
+}
+
+
+static void storvsc_command_completion(struct storvsc_cmd_request *cmd_request,
+				       struct storvsc_device *stor_dev)
+{
+	struct scsi_cmnd *scmnd = cmd_request->cmd;
+	struct scsi_sense_hdr sense_hdr;
+	struct vmscsi_request *vm_srb;
+	u32 data_transfer_length;
+	struct Scsi_Host *host;
+	u32 payload_sz = cmd_request->payload_sz;
+	void *payload = cmd_request->payload;
+	bool sense_ok;
+
+	host = stor_dev->host;
+
+	vm_srb = &cmd_request->vstor_packet.vm_srb;
+	data_transfer_length = vm_srb->data_transfer_length;
+
+	scmnd->result = vm_srb->scsi_status;
+
+	if (scmnd->result) {
+		sense_ok = scsi_normalize_sense(scmnd->sense_buffer,
+				SCSI_SENSE_BUFFERSIZE, &sense_hdr);
+
+		if (sense_ok && do_logging(STORVSC_LOGGING_WARN))
+			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);
+		/*
+		 * The Windows driver set data_transfer_length on
+		 * SRB_STATUS_DATA_OVERRUN. On other errors, this value
+		 * is untouched.  In these cases we set it to 0.
+		 */
+		if (vm_srb->srb_status != SRB_STATUS_DATA_OVERRUN)
+			data_transfer_length = 0;
+	}
+
+	/* Validate data_transfer_length (from Hyper-V) */
+	if (data_transfer_length > cmd_request->payload->range.len)
+		data_transfer_length = cmd_request->payload->range.len;
+
+	scsi_set_resid(scmnd,
+		cmd_request->payload->range.len - data_transfer_length);
+
+	scsi_done(scmnd);
+
+	if (payload_sz >
+		sizeof(struct vmbus_channel_packet_multipage_buffer))
+		kfree(payload);
+}
+
+static void storvsc_on_io_completion(struct storvsc_device *stor_device,
+				  struct vstor_packet *vstor_packet,
+				  struct storvsc_cmd_request *request)
+{
+	struct vstor_packet *stor_pkt;
+	struct hv_device *device = stor_device->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;
+
+	/*
+	 * Copy over the sense_info_length, but limit to the known max
+	 * size if Hyper-V returns a bad value.
+	 */
+	stor_pkt->vm_srb.sense_info_length = min_t(u8, STORVSC_SENSE_BUFFER_SIZE,
+		vstor_packet->vm_srb.sense_info_length);
+
+	if (vstor_packet->vm_srb.scsi_status != 0 ||
+	    vstor_packet->vm_srb.srb_status != SRB_STATUS_SUCCESS) {
+
+		/*
+		 * Log TEST_UNIT_READY errors only as warnings. Hyper-V can
+		 * return errors when detecting devices using TEST_UNIT_READY,
+		 * and logging these as errors produces unhelpful noise.
+		 */
+		int loglevel = (stor_pkt->vm_srb.cdb[0] == TEST_UNIT_READY) ?
+			STORVSC_LOGGING_WARN : STORVSC_LOGGING_ERROR;
+
+		storvsc_log(device, loglevel,
+			"tag#%d cmd 0x%x status: scsi 0x%x srb 0x%x hv 0x%x\n",
+			scsi_cmd_to_rq(request->cmd)->tag,
+			stor_pkt->vm_srb.cdb[0],
+			vstor_packet->vm_srb.scsi_status,
+			vstor_packet->vm_srb.srb_status,
+			vstor_packet->status);
+	}
+
+	if (vstor_packet->vm_srb.scsi_status == SAM_STAT_CHECK_CONDITION &&
+	    (vstor_packet->vm_srb.srb_status & SRB_STATUS_AUTOSENSE_VALID))
+		memcpy(request->cmd->sense_buffer,
+		       vstor_packet->vm_srb.sense_data,
+		       stor_pkt->vm_srb.sense_info_length);
+
+	stor_pkt->vm_srb.data_transfer_length =
+		vstor_packet->vm_srb.data_transfer_length;
+
+	storvsc_command_completion(request, stor_device);
+
+	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 storvsc_device *stor_device,
+			     struct vstor_packet *vstor_packet,
+			     struct storvsc_cmd_request *request)
+{
+	struct hv_host_device *host_dev;
+	switch (vstor_packet->operation) {
+	case VSTOR_OPERATION_COMPLETE_IO:
+		storvsc_on_io_completion(stor_device, vstor_packet, request);
+		break;
+
+	case VSTOR_OPERATION_REMOVE_DEVICE:
+	case VSTOR_OPERATION_ENUMERATE_BUS:
+		host_dev = shost_priv(stor_device->host);
+		queue_work(
+			host_dev->handle_error_wq, &host_dev->host_scan_work);
+		break;
+
+	case VSTOR_OPERATION_FCHBA_DATA:
+		cache_wwn(stor_device, vstor_packet);
+#if IS_ENABLED(CONFIG_SCSI_FC_ATTRS)
+		fc_host_node_name(stor_device->host) = stor_device->node_name;
+		fc_host_port_name(stor_device->host) = stor_device->port_name;
+#endif
+		break;
+	default:
+		break;
+	}
+}
+
+static void storvsc_on_channel_callback(void *context)
+{
+	struct vmbus_channel *channel = (struct vmbus_channel *)context;
+	const struct vmpacket_descriptor *desc;
+	struct hv_device *device;
+	struct storvsc_device *stor_device;
+	struct Scsi_Host *shost;
+	unsigned long time_limit = jiffies + msecs_to_jiffies(CALLBACK_TIMEOUT);
+
+	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;
+
+	shost = stor_device->host;
+
+	foreach_vmbus_pkt(desc, channel) {
+		struct vstor_packet *packet = hv_pkt_data(desc);
+		struct storvsc_cmd_request *request = NULL;
+		u32 pktlen = hv_pkt_datalen(desc);
+		u64 rqst_id = desc->trans_id;
+		u32 minlen = rqst_id ? sizeof(struct vstor_packet) :
+			sizeof(enum vstor_packet_operation);
+
+		if (unlikely(time_after(jiffies, time_limit))) {
+			hv_pkt_iter_close(channel);
+			return;
+		}
+
+		if (pktlen < minlen) {
+			dev_err(&device->device,
+				"Invalid pkt: id=%llu, len=%u, minlen=%u\n",
+				rqst_id, pktlen, minlen);
+			continue;
+		}
+
+		if (rqst_id == VMBUS_RQST_INIT) {
+			request = &stor_device->init_request;
+		} else if (rqst_id == VMBUS_RQST_RESET) {
+			request = &stor_device->reset_request;
+		} else {
+			/* Hyper-V can send an unsolicited message with ID of 0 */
+			if (rqst_id == 0) {
+				/*
+				 * storvsc_on_receive() looks at the vstor_packet in the message
+				 * from the ring buffer.
+				 *
+				 * - If the operation in the vstor_packet is COMPLETE_IO, then
+				 *   we call storvsc_on_io_completion(), and dereference the
+				 *   guest memory address.  Make sure we don't call
+				 *   storvsc_on_io_completion() with a guest memory address
+				 *   that is zero if Hyper-V were to construct and send such
+				 *   a bogus packet.
+				 *
+				 * - If the operation in the vstor_packet is FCHBA_DATA, then
+				 *   we call cache_wwn(), and access the data payload area of
+				 *   the packet (wwn_packet); however, there is no guarantee
+				 *   that the packet is big enough to contain such area.
+				 *   Future-proof the code by rejecting such a bogus packet.
+				 */
+				if (packet->operation == VSTOR_OPERATION_COMPLETE_IO ||
+				    packet->operation == VSTOR_OPERATION_FCHBA_DATA) {
+					dev_err(&device->device, "Invalid packet with ID of 0\n");
+					continue;
+				}
+			} else {
+				struct scsi_cmnd *scmnd;
+
+				/* Transaction 'rqst_id' corresponds to tag 'rqst_id - 1' */
+				scmnd = scsi_host_find_tag(shost, rqst_id - 1);
+				if (scmnd == NULL) {
+					dev_err(&device->device, "Incorrect transaction ID\n");
+					continue;
+				}
+				request = (struct storvsc_cmd_request *)scsi_cmd_priv(scmnd);
+				scsi_dma_unmap(scmnd);
+			}
+
+			storvsc_on_receive(stor_device, packet, request);
+			continue;
+		}
+
+		memcpy(&request->vstor_packet, packet,
+		       sizeof(struct vstor_packet));
+		complete(&request->wait_event);
+	}
+}
+
+static int storvsc_connect_to_vsp(struct hv_device *device, u32 ring_size,
+				  bool is_fc)
+{
+	struct vmstorage_channel_properties props;
+	int ret;
+
+	memset(&props, 0, sizeof(struct vmstorage_channel_properties));
+
+	device->channel->max_pkt_size = STORVSC_MAX_PKT_SIZE;
+	device->channel->next_request_id_callback = storvsc_next_request_id;
+
+	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, is_fc);
+
+	return ret;
+}
+
+static int storvsc_dev_remove(struct hv_device *device)
+{
+	struct storvsc_device *stor_device;
+
+	stor_device = hv_get_drvdata(device);
+
+	stor_device->destroy = true;
+
+	/* Make sure flag is set before waiting */
+	wmb();
+
+	/*
+	 * 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.
+	 */
+	hv_set_drvdata(device, NULL);
+
+	/* Close the channel */
+	vmbus_close(device->channel);
+
+	kfree(stor_device->stor_chns);
+	kfree(stor_device);
+	return 0;
+}
+
+static struct vmbus_channel *get_og_chn(struct storvsc_device *stor_device,
+					u16 q_num)
+{
+	u16 slot = 0;
+	u16 hash_qnum;
+	const struct cpumask *node_mask;
+	int num_channels, tgt_cpu;
+
+	if (stor_device->num_sc == 0) {
+		stor_device->stor_chns[q_num] = stor_device->device->channel;
+		return stor_device->device->channel;
+	}
+
+	/*
+	 * Our channel array is sparsley populated and we
+	 * initiated I/O on a processor/hw-q that does not
+	 * currently have a designated channel. Fix this.
+	 * The strategy is simple:
+	 * I. Ensure NUMA locality
+	 * II. Distribute evenly (best effort)
+	 */
+
+	node_mask = cpumask_of_node(cpu_to_node(q_num));
+
+	num_channels = 0;
+	for_each_cpu(tgt_cpu, &stor_device->alloced_cpus) {
+		if (cpumask_test_cpu(tgt_cpu, node_mask))
+			num_channels++;
+	}
+	if (num_channels == 0) {
+		stor_device->stor_chns[q_num] = stor_device->device->channel;
+		return stor_device->device->channel;
+	}
+
+	hash_qnum = q_num;
+	while (hash_qnum >= num_channels)
+		hash_qnum -= num_channels;
+
+	for_each_cpu(tgt_cpu, &stor_device->alloced_cpus) {
+		if (!cpumask_test_cpu(tgt_cpu, node_mask))
+			continue;
+		if (slot == hash_qnum)
+			break;
+		slot++;
+	}
+
+	stor_device->stor_chns[q_num] = stor_device->stor_chns[tgt_cpu];
+
+	return stor_device->stor_chns[q_num];
+}
+
+
+static int storvsc_do_io(struct hv_device *device,
+			 struct storvsc_cmd_request *request, u16 q_num)
+{
+	struct storvsc_device *stor_device;
+	struct vstor_packet *vstor_packet;
+	struct vmbus_channel *outgoing_channel, *channel;
+	unsigned long flags;
+	int ret = 0;
+	const struct cpumask *node_mask;
+	int tgt_cpu;
+
+	vstor_packet = &request->vstor_packet;
+	stor_device = get_out_stor_device(device);
+
+	if (!stor_device)
+		return -ENODEV;
+
+
+	request->device  = device;
+	/*
+	 * Select an appropriate channel to send the request out.
+	 */
+	/* See storvsc_change_target_cpu(). */
+	outgoing_channel = READ_ONCE(stor_device->stor_chns[q_num]);
+	if (outgoing_channel != NULL) {
+		if (outgoing_channel->target_cpu == q_num) {
+			/*
+			 * Ideally, we want to pick a different channel if
+			 * available on the same NUMA node.
+			 */
+			node_mask = cpumask_of_node(cpu_to_node(q_num));
+			for_each_cpu_wrap(tgt_cpu,
+				 &stor_device->alloced_cpus, q_num + 1) {
+				if (!cpumask_test_cpu(tgt_cpu, node_mask))
+					continue;
+				if (tgt_cpu == q_num)
+					continue;
+				channel = READ_ONCE(
+					stor_device->stor_chns[tgt_cpu]);
+				if (channel == NULL)
+					continue;
+				if (hv_get_avail_to_write_percent(
+							&channel->outbound)
+						> ring_avail_percent_lowater) {
+					outgoing_channel = channel;
+					goto found_channel;
+				}
+			}
+
+			/*
+			 * All the other channels on the same NUMA node are
+			 * busy. Try to use the channel on the current CPU
+			 */
+			if (hv_get_avail_to_write_percent(
+						&outgoing_channel->outbound)
+					> ring_avail_percent_lowater)
+				goto found_channel;
+
+			/*
+			 * If we reach here, all the channels on the current
+			 * NUMA node are busy. Try to find a channel in
+			 * other NUMA nodes
+			 */
+			for_each_cpu(tgt_cpu, &stor_device->alloced_cpus) {
+				if (cpumask_test_cpu(tgt_cpu, node_mask))
+					continue;
+				channel = READ_ONCE(
+					stor_device->stor_chns[tgt_cpu]);
+				if (channel == NULL)
+					continue;
+				if (hv_get_avail_to_write_percent(
+							&channel->outbound)
+						> ring_avail_percent_lowater) {
+					outgoing_channel = channel;
+					goto found_channel;
+				}
+			}
+		}
+	} else {
+		spin_lock_irqsave(&stor_device->lock, flags);
+		outgoing_channel = stor_device->stor_chns[q_num];
+		if (outgoing_channel != NULL) {
+			spin_unlock_irqrestore(&stor_device->lock, flags);
+			goto found_channel;
+		}
+		outgoing_channel = get_og_chn(stor_device, q_num);
+		spin_unlock_irqrestore(&stor_device->lock, flags);
+	}
+
+found_channel:
+	vstor_packet->flags |= REQUEST_COMPLETION_FLAG;
+
+	vstor_packet->vm_srb.length = sizeof(struct vmscsi_request);
+
+
+	vstor_packet->vm_srb.sense_info_length = STORVSC_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),
+				(unsigned long)request);
+	} else {
+		ret = vmbus_sendpacket(outgoing_channel, vstor_packet,
+			       sizeof(struct vstor_packet),
+			       (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_alloc(struct scsi_device *sdevice)
+{
+	/*
+	 * Set blist flag 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 flag we can correctly handle WRITE_SAME_16 issues.
+	 *
+	 * Hypervisor reports SCSI_UNKNOWN type for DVD ROM device but
+	 * still supports REPORT LUN.
+	 */
+	sdevice->sdev_bflags = BLIST_REPORTLUN2 | BLIST_TRY_VPD_PAGES;
+
+	return 0;
+}
+
+static int storvsc_device_configure(struct scsi_device *sdevice)
+{
+	blk_queue_rq_timeout(sdevice->request_queue, (storvsc_timeout * HZ));
+
+	/* storvsc devices don't support MAINTENANCE_IN SCSI cmd */
+	sdevice->no_report_opcodes = 1;
+	sdevice->no_write_same = 1;
+
+	/*
+	 * 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;
+	memset(vstor_packet, 0, sizeof(struct 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),
+			       VMBUS_RQST_RESET,
+			       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:
+		set_host_byte(scmnd, DID_ERROR);
+		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);
+	struct scatterlist *sgl;
+	struct vmscsi_request *vm_srb;
+	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)) {
+			scsi_done(scmnd);
+			return 0;
+		}
+	}
+
+	/* Setup the cmd request */
+	cmd_request->cmd = scmnd;
+
+	memset(&cmd_request->vstor_packet, 0, sizeof(struct vstor_packet));
+	vm_srb = &cmd_request->vstor_packet.vm_srb;
+	vm_srb->time_out_value = 60;
+
+	vm_srb->srb_flags |=
+		SRB_FLAGS_DISABLE_SYNCH_TRANSFER;
+
+	if (scmnd->device->tagged_supported) {
+		vm_srb->srb_flags |=
+		(SRB_FLAGS_QUEUE_ACTION_ENABLE | SRB_FLAGS_NO_QUEUE_FREEZE);
+		vm_srb->queue_tag = SP_UNTAGGED;
+		vm_srb->queue_action = SRB_SIMPLE_TAG_REQUEST;
+	}
+
+	/* Build the SRB */
+	switch (scmnd->sc_data_direction) {
+	case DMA_TO_DEVICE:
+		vm_srb->data_in = WRITE_TYPE;
+		vm_srb->srb_flags |= SRB_FLAGS_DATA_OUT;
+		break;
+	case DMA_FROM_DEVICE:
+		vm_srb->data_in = READ_TYPE;
+		vm_srb->srb_flags |= SRB_FLAGS_DATA_IN;
+		break;
+	case DMA_NONE:
+		vm_srb->data_in = UNKNOWN_TYPE;
+		vm_srb->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);
+
+	length = scsi_bufflen(scmnd);
+	payload = (struct vmbus_packet_mpb_array *)&cmd_request->mpb;
+	payload_sz = 0;
+
+	if (scsi_sg_count(scmnd)) {
+		unsigned long offset_in_hvpg = offset_in_hvpage(sgl->offset);
+		unsigned int hvpg_count = HVPFN_UP(offset_in_hvpg + length);
+		struct scatterlist *sg;
+		unsigned long hvpfn, hvpfns_to_add;
+		int j, i = 0, sg_count;
+
+		payload_sz = (hvpg_count * sizeof(u64) +
+			      sizeof(struct vmbus_packet_mpb_array));
+
+		if (hvpg_count > MAX_PAGE_BUFFER_COUNT) {
+			payload = kzalloc(payload_sz, GFP_ATOMIC);
+			if (!payload)
+				return SCSI_MLQUEUE_DEVICE_BUSY;
+		}
+
+		payload->range.len = length;
+		payload->range.offset = offset_in_hvpg;
+
+		sg_count = scsi_dma_map(scmnd);
+		if (sg_count < 0) {
+			ret = SCSI_MLQUEUE_DEVICE_BUSY;
+			goto err_free_payload;
+		}
+
+		for_each_sg(sgl, sg, sg_count, j) {
+			/*
+			 * Init values for the current sgl entry. hvpfns_to_add
+			 * is in units of Hyper-V size pages. Handling the
+			 * PAGE_SIZE != HV_HYP_PAGE_SIZE case also handles
+			 * values of sgl->offset that are larger than PAGE_SIZE.
+			 * Such offsets are handled even on other than the first
+			 * sgl entry, provided they are a multiple of PAGE_SIZE.
+			 */
+			hvpfn = HVPFN_DOWN(sg_dma_address(sg));
+			hvpfns_to_add = HVPFN_UP(sg_dma_address(sg) +
+						 sg_dma_len(sg)) - hvpfn;
+
+			/*
+			 * Fill the next portion of the PFN array with
+			 * sequential Hyper-V PFNs for the continguous physical
+			 * memory described by the sgl entry. The end of the
+			 * last sgl should be reached at the same time that
+			 * the PFN array is filled.
+			 */
+			while (hvpfns_to_add--)
+				payload->range.pfn_array[i++] = hvpfn++;
+		}
+	}
+
+	cmd_request->payload = payload;
+	cmd_request->payload_sz = payload_sz;
+
+	/* Invokes the vsc to start an IO */
+	ret = storvsc_do_io(dev, cmd_request, get_cpu());
+	put_cpu();
+
+	if (ret)
+		scsi_dma_unmap(scmnd);
+
+	if (ret == -EAGAIN) {
+		/* no more space */
+		ret = SCSI_MLQUEUE_DEVICE_BUSY;
+		goto err_free_payload;
+	}
+
+	return 0;
+
+err_free_payload:
+	if (payload_sz > sizeof(cmd_request->mpb))
+		kfree(payload);
+
+	return ret;
+}
+
+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_alloc =		storvsc_device_alloc,
+	.slave_configure =	storvsc_device_configure,
+	.cmd_per_lun =		2048,
+	.this_id =		-1,
+	/* Ensure there are no gaps in presented sgls */
+	.virt_boundary_mask =	HV_HYP_PAGE_SIZE - 1,
+	.no_write_same =	1,
+	.track_queue_depth =	1,
+	.change_queue_depth =	storvsc_change_queue_depth,
+};
+
+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 const struct { guid_t guid; } fc_guid = { HV_SYNTHFC_GUID };
+
+static bool hv_dev_is_fc(struct hv_device *hv_dev)
+{
+	return guid_equal(&fc_guid.guid, &hv_dev->dev_type);
+}
+
+static int storvsc_probe(struct hv_device *device,
+			const struct hv_vmbus_device_id *dev_id)
+{
+	int ret;
+	int num_cpus = num_online_cpus();
+	int num_present_cpus = num_present_cpus();
+	struct Scsi_Host *host;
+	struct hv_host_device *host_dev;
+	bool dev_is_ide = ((dev_id->driver_data == IDE_GUID) ? true : false);
+	bool is_fc = ((dev_id->driver_data == SFC_GUID) ? true : false);
+	int target = 0;
+	struct storvsc_device *stor_device;
+	int max_sub_channels = 0;
+	u32 max_xfer_bytes;
+
+	/*
+	 * We support sub-channels for storage on SCSI and FC controllers.
+	 * The number of sub-channels offerred is based on the number of
+	 * VCPUs in the guest.
+	 */
+	if (!dev_is_ide)
+		max_sub_channels =
+			(num_cpus - 1) / storvsc_vcpus_per_sub_channel;
+
+	scsi_driver.can_queue = max_outstanding_req_per_channel *
+				(max_sub_channels + 1) *
+				(100 - ring_avail_percent_lowater) / 100;
+
+	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;
+	host_dev->host = host;
+
+
+	stor_device = kzalloc(sizeof(struct storvsc_device), GFP_KERNEL);
+	if (!stor_device) {
+		ret = -ENOMEM;
+		goto err_out0;
+	}
+
+	stor_device->destroy = false;
+	init_waitqueue_head(&stor_device->waiting_to_drain);
+	stor_device->device = device;
+	stor_device->host = host;
+	spin_lock_init(&stor_device->lock);
+	hv_set_drvdata(device, stor_device);
+	dma_set_min_align_mask(&device->device, HV_HYP_PAGE_SIZE - 1);
+
+	stor_device->port_number = host->host_no;
+	ret = storvsc_connect_to_vsp(device, storvsc_ringbuffer_size, is_fc);
+	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;
+#if IS_ENABLED(CONFIG_SCSI_FC_ATTRS)
+		host->transportt = fc_transport_template;
+#endif
+		break;
+
+	case SCSI_GUID:
+		host->max_lun = STORVSC_MAX_LUNS_PER_TARGET;
+		host->max_id = STORVSC_MAX_TARGETS;
+		host->max_channel = STORVSC_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;
+	/*
+	 * Any reasonable Hyper-V configuration should provide
+	 * max_transfer_bytes value aligning to HV_HYP_PAGE_SIZE,
+	 * protecting it from any weird value.
+	 */
+	max_xfer_bytes = round_down(stor_device->max_transfer_bytes, HV_HYP_PAGE_SIZE);
+	if (is_fc)
+		max_xfer_bytes = min(max_xfer_bytes, STORVSC_FC_MAX_XFER_SIZE);
+
+	/* max_hw_sectors_kb */
+	host->max_sectors = max_xfer_bytes >> 9;
+	/*
+	 * There are 2 requirements for Hyper-V storvsc sgl segments,
+	 * based on which the below calculation for max segments is
+	 * done:
+	 *
+	 * 1. Except for the first and last sgl segment, all sgl segments
+	 *    should be align to HV_HYP_PAGE_SIZE, that also means the
+	 *    maximum number of segments in a sgl can be calculated by
+	 *    dividing the total max transfer length by HV_HYP_PAGE_SIZE.
+	 *
+	 * 2. Except for the first and last, each entry in the SGL must
+	 *    have an offset that is a multiple of HV_HYP_PAGE_SIZE.
+	 */
+	host->sg_tablesize = (max_xfer_bytes >> HV_HYP_PAGE_SHIFT) + 1;
+	/*
+	 * For non-IDE disks, the host supports multiple channels.
+	 * Set the number of HW queues we are supporting.
+	 */
+	if (!dev_is_ide) {
+		if (storvsc_max_hw_queues > num_present_cpus) {
+			storvsc_max_hw_queues = 0;
+			storvsc_log(device, STORVSC_LOGGING_WARN,
+				"Resetting invalid storvsc_max_hw_queues value to default.\n");
+		}
+		if (storvsc_max_hw_queues)
+			host->nr_hw_queues = storvsc_max_hw_queues;
+		else
+			host->nr_hw_queues = num_present_cpus;
+	}
+
+	/*
+	 * Set the error handler work queue.
+	 */
+	host_dev->handle_error_wq =
+			alloc_ordered_workqueue("storvsc_error_wq_%d",
+						0,
+						host->host_no);
+	if (!host_dev->handle_error_wq) {
+		ret = -ENOMEM;
+		goto err_out2;
+	}
+	INIT_WORK(&host_dev->host_scan_work, storvsc_host_scan);
+	/* Register the HBA and start the scsi bus scan */
+	ret = scsi_add_host(host, &device->device);
+	if (ret != 0)
+		goto err_out3;
+
+	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)
+			goto err_out4;
+	}
+#if IS_ENABLED(CONFIG_SCSI_FC_ATTRS)
+	if (host->transportt == fc_transport_template) {
+		struct fc_rport_identifiers ids = {
+			.roles = FC_PORT_ROLE_FCP_DUMMY_INITIATOR,
+		};
+
+		fc_host_node_name(host) = stor_device->node_name;
+		fc_host_port_name(host) = stor_device->port_name;
+		stor_device->rport = fc_remote_port_add(host, 0, &ids);
+		if (!stor_device->rport) {
+			ret = -ENOMEM;
+			goto err_out4;
+		}
+	}
+#endif
+	return 0;
+
+err_out4:
+	scsi_remove_host(host);
+
+err_out3:
+	destroy_workqueue(host_dev->handle_error_wq);
+
+err_out2:
+	/*
+	 * Once we have connected with the host, we would need 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->stor_chns);
+	kfree(stor_device);
+
+err_out0:
+	scsi_host_put(host);
+	return ret;
+}
+
+/* Change a scsi target's queue depth */
+static int storvsc_change_queue_depth(struct scsi_device *sdev, int queue_depth)
+{
+	if (queue_depth > scsi_driver.can_queue)
+		queue_depth = scsi_driver.can_queue;
+
+	return scsi_change_queue_depth(sdev, queue_depth);
+}
+
+static int storvsc_remove(struct hv_device *dev)
+{
+	struct storvsc_device *stor_device = hv_get_drvdata(dev);
+	struct Scsi_Host *host = stor_device->host;
+	struct hv_host_device *host_dev = shost_priv(host);
+
+#if IS_ENABLED(CONFIG_SCSI_FC_ATTRS)
+	if (host->transportt == fc_transport_template) {
+		fc_remote_port_delete(stor_device->rport);
+		fc_remove_host(host);
+	}
+#endif
+	destroy_workqueue(host_dev->handle_error_wq);
+	scsi_remove_host(host);
+	storvsc_dev_remove(dev);
+	scsi_host_put(host);
+
+	return 0;
+}
+
+static int storvsc_suspend(struct hv_device *hv_dev)
+{
+	struct storvsc_device *stor_device = hv_get_drvdata(hv_dev);
+	struct Scsi_Host *host = stor_device->host;
+	struct hv_host_device *host_dev = shost_priv(host);
+
+	storvsc_wait_to_drain(stor_device);
+
+	drain_workqueue(host_dev->handle_error_wq);
+
+	vmbus_close(hv_dev->channel);
+
+	kfree(stor_device->stor_chns);
+	stor_device->stor_chns = NULL;
+
+	cpumask_clear(&stor_device->alloced_cpus);
+
+	return 0;
+}
+
+static int storvsc_resume(struct hv_device *hv_dev)
+{
+	int ret;
+
+	ret = storvsc_connect_to_vsp(hv_dev, storvsc_ringbuffer_size,
+				     hv_dev_is_fc(hv_dev));
+	return ret;
+}
+
+static struct hv_driver storvsc_drv = {
+	.name = KBUILD_MODNAME,
+	.id_table = id_table,
+	.probe = storvsc_probe,
+	.remove = storvsc_remove,
+	.suspend = storvsc_suspend,
+	.resume = storvsc_resume,
+	.driver = {
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+
+#if IS_ENABLED(CONFIG_SCSI_FC_ATTRS)
+static struct fc_function_template fc_transport_functions = {
+	.show_host_node_name = 1,
+	.show_host_port_name = 1,
+};
+#endif
+
+static int __init storvsc_drv_init(void)
+{
+	int ret;
+
+	/*
+	 * 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),
+		sizeof(u64)));
+
+#if IS_ENABLED(CONFIG_SCSI_FC_ATTRS)
+	fc_transport_template = fc_attach_transport(&fc_transport_functions);
+	if (!fc_transport_template)
+		return -ENODEV;
+#endif
+
+	ret = vmbus_driver_register(&storvsc_drv);
+
+#if IS_ENABLED(CONFIG_SCSI_FC_ATTRS)
+	if (ret)
+		fc_release_transport(fc_transport_template);
+#endif
+
+	return ret;
+}
+
+static void __exit storvsc_drv_exit(void)
+{
+	vmbus_driver_unregister(&storvsc_drv);
+#if IS_ENABLED(CONFIG_SCSI_FC_ATTRS)
+	fc_release_transport(fc_transport_template);
+#endif
+}
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Microsoft Hyper-V virtual storage driver");
+module_init(storvsc_drv_init);
+module_exit(storvsc_drv_exit);