Initial import

1 files changed, 1935 insertions, 0 deletions

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
new file mode 100644
index 000000000..3c6584ff6
--- /dev/null
+++ b/drivers/scsi/storvsc_drv.c
@@ -0,0 +1,1935 @@
+/*
+ * 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
+ */
+
+
+#define VMSTOR_WIN7_MAJOR 4
+#define VMSTOR_WIN7_MINOR 2
+
+#define VMSTOR_WIN8_MAJOR 5
+#define VMSTOR_WIN8_MINOR 1
+
+
+/*  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.
+ */
+static int sense_buffer_size;
+
+/*
+ * 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.
+ */
+
+static int vmscsi_size_delta;
+static int vmstor_current_major;
+static int vmstor_current_minor;
+
+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));
+
+
+/*
+ * 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_INVALID_LUN	0x20
+#define SRB_STATUS_SUCCESS	0x01
+#define SRB_STATUS_ABORTED	0x02
+#define SRB_STATUS_ERROR	0x04
+
+/*
+ * 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;
+
+	unsigned int bounce_sgl_count;
+	struct scatterlist *bounce_sgl;
+
+	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;
+	unsigned long flags;
+
+	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);
+	spin_lock_irqsave(host->host_lock, flags);
+	list_for_each_entry(sdev, &host->__devices, siblings) {
+		spin_unlock_irqrestore(host->host_lock, flags);
+		scsi_test_unit_ready(sdev, 1, 1, NULL);
+		spin_lock_irqsave(host->host_lock, flags);
+		continue;
+	}
+	spin_unlock_irqrestore(host->host_lock, flags);
+	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);
+}
+
+/*
+ * Major/minor macros.  Minor version is in LSB, meaning that earlier flat
+ * version numbers will be interpreted as "0.x" (i.e., 1 becomes 0.1).
+ */
+
+static inline u16 storvsc_get_version(u8 major, u8 minor)
+{
+	u16 version;
+
+	version = ((major << 8) | minor);
+	return version;
+}
+
+/*
+ * 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 destroy_bounce_buffer(struct scatterlist *sgl,
+				  unsigned int sg_count)
+{
+	int i;
+	struct page *page_buf;
+
+	for (i = 0; i < sg_count; i++) {
+		page_buf = sg_page((&sgl[i]));
+		if (page_buf != NULL)
+			__free_page(page_buf);
+	}
+
+	kfree(sgl);
+}
+
+static int do_bounce_buffer(struct scatterlist *sgl, unsigned int sg_count)
+{
+	int i;
+
+	/* No need to check */
+	if (sg_count < 2)
+		return -1;
+
+	/* We have at least 2 sg entries */
+	for (i = 0; i < sg_count; i++) {
+		if (i == 0) {
+			/* make sure 1st one does not have hole */
+			if (sgl[i].offset + sgl[i].length != PAGE_SIZE)
+				return i;
+		} else if (i == sg_count - 1) {
+			/* make sure last one does not have hole */
+			if (sgl[i].offset != 0)
+				return i;
+		} else {
+			/* make sure no hole in the middle */
+			if (sgl[i].length != PAGE_SIZE || sgl[i].offset != 0)
+				return i;
+		}
+	}
+	return -1;
+}
+
+static struct scatterlist *create_bounce_buffer(struct scatterlist *sgl,
+						unsigned int sg_count,
+						unsigned int len,
+						int write)
+{
+	int i;
+	int num_pages;
+	struct scatterlist *bounce_sgl;
+	struct page *page_buf;
+	unsigned int buf_len = ((write == WRITE_TYPE) ? 0 : PAGE_SIZE);
+
+	num_pages = ALIGN(len, PAGE_SIZE) >> PAGE_SHIFT;
+
+	bounce_sgl = kcalloc(num_pages, sizeof(struct scatterlist), GFP_ATOMIC);
+	if (!bounce_sgl)
+		return NULL;
+
+	sg_init_table(bounce_sgl, num_pages);
+	for (i = 0; i < num_pages; i++) {
+		page_buf = alloc_page(GFP_ATOMIC);
+		if (!page_buf)
+			goto cleanup;
+		sg_set_page(&bounce_sgl[i], page_buf, buf_len, 0);
+	}
+
+	return bounce_sgl;
+
+cleanup:
+	destroy_bounce_buffer(bounce_sgl, num_pages);
+	return NULL;
+}
+
+/* Assume the original sgl has enough room */
+static unsigned int copy_from_bounce_buffer(struct scatterlist *orig_sgl,
+					    struct scatterlist *bounce_sgl,
+					    unsigned int orig_sgl_count,
+					    unsigned int bounce_sgl_count)
+{
+	int i;
+	int j = 0;
+	unsigned long src, dest;
+	unsigned int srclen, destlen, copylen;
+	unsigned int total_copied = 0;
+	unsigned long bounce_addr = 0;
+	unsigned long dest_addr = 0;
+	unsigned long flags;
+	struct scatterlist *cur_dest_sgl;
+	struct scatterlist *cur_src_sgl;
+
+	local_irq_save(flags);
+	cur_dest_sgl = orig_sgl;
+	cur_src_sgl = bounce_sgl;
+	for (i = 0; i < orig_sgl_count; i++) {
+		dest_addr = (unsigned long)
+				kmap_atomic(sg_page(cur_dest_sgl)) +
+				cur_dest_sgl->offset;
+		dest = dest_addr;
+		destlen = cur_dest_sgl->length;
+
+		if (bounce_addr == 0)
+			bounce_addr = (unsigned long)kmap_atomic(
+							sg_page(cur_src_sgl));
+
+		while (destlen) {
+			src = bounce_addr + cur_src_sgl->offset;
+			srclen = cur_src_sgl->length - cur_src_sgl->offset;
+
+			copylen = min(srclen, destlen);
+			memcpy((void *)dest, (void *)src, copylen);
+
+			total_copied += copylen;
+			cur_src_sgl->offset += copylen;
+			destlen -= copylen;
+			dest += copylen;
+
+			if (cur_src_sgl->offset == cur_src_sgl->length) {
+				/* full */
+				kunmap_atomic((void *)bounce_addr);
+				j++;
+
+				/*
+				 * It is possible that the number of elements
+				 * in the bounce buffer may not be equal to
+				 * the number of elements in the original
+				 * scatter list. Handle this correctly.
+				 */
+
+				if (j == bounce_sgl_count) {
+					/*
+					 * We are done; cleanup and return.
+					 */
+					kunmap_atomic((void *)(dest_addr -
+						cur_dest_sgl->offset));
+					local_irq_restore(flags);
+					return total_copied;
+				}
+
+				/* if we need to use another bounce buffer */
+				if (destlen || i != orig_sgl_count - 1) {
+					cur_src_sgl = sg_next(cur_src_sgl);
+					bounce_addr = (unsigned long)
+							kmap_atomic(
+							sg_page(cur_src_sgl));
+				}
+			} else if (destlen == 0 && i == orig_sgl_count - 1) {
+				/* unmap the last bounce that is < PAGE_SIZE */
+				kunmap_atomic((void *)bounce_addr);
+			}
+		}
+
+		kunmap_atomic((void *)(dest_addr - cur_dest_sgl->offset));
+		cur_dest_sgl = sg_next(cur_dest_sgl);
+	}
+
+	local_irq_restore(flags);
+
+	return total_copied;
+}
+
+/* Assume the bounce_sgl has enough room ie using the create_bounce_buffer() */
+static unsigned int copy_to_bounce_buffer(struct scatterlist *orig_sgl,
+					  struct scatterlist *bounce_sgl,
+					  unsigned int orig_sgl_count)
+{
+	int i;
+	int j = 0;
+	unsigned long src, dest;
+	unsigned int srclen, destlen, copylen;
+	unsigned int total_copied = 0;
+	unsigned long bounce_addr = 0;
+	unsigned long src_addr = 0;
+	unsigned long flags;
+	struct scatterlist *cur_src_sgl;
+	struct scatterlist *cur_dest_sgl;
+
+	local_irq_save(flags);
+
+	cur_src_sgl = orig_sgl;
+	cur_dest_sgl = bounce_sgl;
+
+	for (i = 0; i < orig_sgl_count; i++) {
+		src_addr = (unsigned long)
+				kmap_atomic(sg_page(cur_src_sgl)) +
+				cur_src_sgl->offset;
+		src = src_addr;
+		srclen = cur_src_sgl->length;
+
+		if (bounce_addr == 0)
+			bounce_addr = (unsigned long)
+					kmap_atomic(sg_page(cur_dest_sgl));
+
+		while (srclen) {
+			/* assume bounce offset always == 0 */
+			dest = bounce_addr + cur_dest_sgl->length;
+			destlen = PAGE_SIZE - cur_dest_sgl->length;
+
+			copylen = min(srclen, destlen);
+			memcpy((void *)dest, (void *)src, copylen);
+
+			total_copied += copylen;
+			cur_dest_sgl->length += copylen;
+			srclen -= copylen;
+			src += copylen;
+
+			if (cur_dest_sgl->length == PAGE_SIZE) {
+				/* full..move to next entry */
+				kunmap_atomic((void *)bounce_addr);
+				bounce_addr = 0;
+				j++;
+			}
+
+			/* if we need to use another bounce buffer */
+			if (srclen && bounce_addr == 0) {
+				cur_dest_sgl = sg_next(cur_dest_sgl);
+				bounce_addr = (unsigned long)
+						kmap_atomic(
+						sg_page(cur_dest_sgl));
+			}
+
+		}
+
+		kunmap_atomic((void *)(src_addr - cur_src_sgl->offset));
+		cur_src_sgl = sg_next(cur_src_sgl);
+	}
+
+	if (bounce_addr)
+		kunmap_atomic((void *)bounce_addr);
+
+	local_irq_restore(flags);
+
+	return total_copied;
+}
+
+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;
+	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)
+		goto cleanup;
+
+
+	/* 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 =
+		storvsc_get_version(vmstor_current_major, vmstor_current_minor);
+
+	/*
+	 * 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 ||
+	    vstor_packet->status != 0)
+		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)
+		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 ((vmbus_proto_version != VERSION_WIN7) &&
+	   (vmbus_proto_version != VERSION_WS2008))  {
+		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)
+		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 (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;
+	if (cmd_request->bounce_sgl_count) {
+		if (vm_srb->data_in == READ_TYPE)
+			copy_from_bounce_buffer(scsi_sglist(scmnd),
+					cmd_request->bounce_sgl,
+					scsi_sg_count(scmnd),
+					cmd_request->bounce_sgl_count);
+		destroy_bounce_buffer(cmd_request->bounce_sgl,
+					cmd_request->bounce_sgl_count);
+	}
+
+	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));
+
+	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 (!strncmp(sdevice->vendor, "Msft", 4)) {
+		switch (vmbus_proto_version) {
+		case VERSION_WIN8:
+		case VERSION_WIN8_1:
+			sdevice->scsi_level = SCSI_SPC_3;
+			break;
+		}
+	}
+
+	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_current_major <= VMSTOR_WIN8_MAJOR) {
+		/*
+		 * 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_QUEUE_ACTION_ENABLE |
+		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;
+	default:
+		vm_srb->data_in = UNKNOWN_TYPE;
+		vm_srb->win8_extension.srb_flags |= SRB_FLAGS_NO_DATA_TRANSFER;
+		break;
+	}
+
+
+	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) {
+		/* check if we need to bounce the sgl */
+		if (do_bounce_buffer(sgl, scsi_sg_count(scmnd)) != -1) {
+			cmd_request->bounce_sgl =
+				create_bounce_buffer(sgl, sg_count,
+						     length,
+						     vm_srb->data_in);
+			if (!cmd_request->bounce_sgl)
+				return SCSI_MLQUEUE_HOST_BUSY;
+
+			cmd_request->bounce_sgl_count =
+				ALIGN(length, PAGE_SIZE) >> PAGE_SHIFT;
+
+			if (vm_srb->data_in == WRITE_TYPE)
+				copy_to_bounce_buffer(sgl,
+					cmd_request->bounce_sgl, sg_count);
+
+			sgl = cmd_request->bounce_sgl;
+			sg_count = cmd_request->bounce_sgl_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) {
+				if (cmd_request->bounce_sgl_count)
+					destroy_bounce_buffer(
+					cmd_request->bounce_sgl,
+					cmd_request->bounce_sgl_count);
+
+					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 */
+
+		if (cmd_request->bounce_sgl_count)
+			destroy_bounce_buffer(cmd_request->bounce_sgl,
+					cmd_request->bounce_sgl_count);
+
+		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.
+	 */
+
+	switch (vmbus_proto_version) {
+	case VERSION_WS2008:
+	case VERSION_WIN7:
+		sense_buffer_size = PRE_WIN8_STORVSC_SENSE_BUFFER_SIZE;
+		vmscsi_size_delta = sizeof(struct vmscsi_win8_extension);
+		vmstor_current_major = VMSTOR_WIN7_MAJOR;
+		vmstor_current_minor = VMSTOR_WIN7_MINOR;
+		max_luns_per_target = STORVSC_IDE_MAX_LUNS_PER_TARGET;
+		max_targets = STORVSC_IDE_MAX_TARGETS;
+		max_channels = STORVSC_IDE_MAX_CHANNELS;
+		break;
+	default:
+		sense_buffer_size = POST_WIN7_STORVSC_SENSE_BUFFER_SIZE;
+		vmscsi_size_delta = 0;
+		vmstor_current_major = VMSTOR_WIN8_MAJOR;
+		vmstor_current_minor = VMSTOR_WIN8_MINOR;
+		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);
+		break;
+	}
+
+	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);