kernel / include / linux / hyperv.h

/*
 *
 * Copyright (c) 2011, 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 <[e-mail]>
 *   Hank Janssen  <[e-mail]>
 *   K. Y. Srinivasan <[e-mail]>
 *
 */

#ifndef _HYPERV_H
#define _HYPERV_H

#include <uapi/linux/hyperv.h>

#include <linux/types.h>
#include <linux/scatterlist.h>
#include <linux/list.h>
#include <linux/timer.h>
#include <linux/completion.h>
#include <linux/device.h>
#include <linux/mod_devicetable.h>
#include <linux/interrupt.h>
#include <linux/reciprocal_div.h>

#define MAX_PAGE_BUFFER_COUNT				32
#define MAX_MULTIPAGE_BUFFER_COUNT			32 /* 128K */

#pragma pack(push, 1)

/* Single-page buffer */
struct hv_page_buffer {
	u32 len;
	u32 offset;
	u64 pfn;
};

/* Multiple-page buffer */
struct hv_multipage_buffer {
	/* Length and Offset determines the # of pfns in the array */
	u32 len;
	u32 offset;
	u64 pfn_array[MAX_MULTIPAGE_BUFFER_COUNT];
};

/*
 * Multiple-page buffer array; the pfn array is variable size:
 * The number of entries in the PFN array is determined by
 * "len" and "offset".
 */
struct hv_mpb_array {
	/* Length and Offset determines the # of pfns in the array */
	u32 len;
	u32 offset;
	u64 pfn_array[];
};

/* 0x18 includes the proprietary packet header */
#define MAX_PAGE_BUFFER_PACKET		(0x18 +			\
					(sizeof(struct hv_page_buffer) * \
					 MAX_PAGE_BUFFER_COUNT))
#define MAX_MULTIPAGE_BUFFER_PACKET	(0x18 +			\
					 sizeof(struct hv_multipage_buffer))


#pragma pack(pop)

struct hv_ring_buffer {
	/* Offset in bytes from the start of ring data below */
	u32 write_index;

	/* Offset in bytes from the start of ring data below */
	u32 read_index;

	u32 interrupt_mask;

	/*
	 * WS2012/Win8 and later versions of Hyper-V implement interrupt
	 * driven flow management. The feature bit feat_pending_send_sz
	 * is set by the host on the host->guest ring buffer, and by the
	 * guest on the guest->host ring buffer.
	 *
	 * The meaning of the feature bit is a bit complex in that it has
	 * semantics that apply to both ring buffers.  If the guest sets
	 * the feature bit in the guest->host ring buffer, the guest is
	 * telling the host that:
	 * 1) It will set the pending_send_sz field in the guest->host ring
	 *    buffer when it is waiting for space to become available, and
	 * 2) It will read the pending_send_sz field in the host->guest
	 *    ring buffer and interrupt the host when it frees enough space
	 *
	 * Similarly, if the host sets the feature bit in the host->guest
	 * ring buffer, the host is telling the guest that:
	 * 1) It will set the pending_send_sz field in the host->guest ring
	 *    buffer when it is waiting for space to become available, and
	 * 2) It will read the pending_send_sz field in the guest->host
	 *    ring buffer and interrupt the guest when it frees enough space
	 *
	 * If either the guest or host does not set the feature bit that it
	 * owns, that guest or host must do polling if it encounters a full
	 * ring buffer, and not signal the other end with an interrupt.
	 */
	u32 pending_send_sz;
	u32 reserved1[12];
	union {
		struct {
			u32 feat_pending_send_sz:1;
		};
		u32 value;
	} feature_bits;

	/* Pad it to PAGE_SIZE so that data starts on page boundary */
	u8	reserved2[4028];

	/*
	 * Ring data starts here + RingDataStartOffset
	 * !!! DO NOT place any fields below this !!!
	 */
	u8 buffer[0];
} __packed;

struct hv_ring_buffer_info {
	struct hv_ring_buffer *ring_buffer;
	u32 ring_size;			/* Include the shared header */
	struct reciprocal_value ring_size_div10_reciprocal;
	spinlock_t ring_lock;

	u32 ring_datasize;		/* < ring_size */
	u32 priv_read_index;
	/*
	 * The ring buffer mutex lock. This lock prevents the ring buffer from
	 * being freed while the ring buffer is being accessed.
	 */
	struct mutex ring_buffer_mutex;
};


static inline u32 hv_get_bytes_to_read(const struct hv_ring_buffer_info *rbi)
{
	u32 read_loc, write_loc, dsize, read;

	dsize = rbi->ring_datasize;
	read_loc = rbi->ring_buffer->read_index;
	write_loc = READ_ONCE(rbi->ring_buffer->write_index);

	read = write_loc >= read_loc ? (write_loc - read_loc) :
		(dsize - read_loc) + write_loc;

	return read;
}

static inline u32 hv_get_bytes_to_write(const struct hv_ring_buffer_info *rbi)
{
	u32 read_loc, write_loc, dsize, write;

	dsize = rbi->ring_datasize;
	read_loc = READ_ONCE(rbi->ring_buffer->read_index);
	write_loc = rbi->ring_buffer->write_index;

	write = write_loc >= read_loc ? dsize - (write_loc - read_loc) :
		read_loc - write_loc;
	return write;
}

static inline u32 hv_get_avail_to_write_percent(
		const struct hv_ring_buffer_info *rbi)
{
	u32 avail_write = hv_get_bytes_to_write(rbi);

	return reciprocal_divide(
			(avail_write  << 3) + (avail_write << 1),
			rbi->ring_size_div10_reciprocal);
}

/*
 * VMBUS version is 32 bit entity broken up into
 * two 16 bit quantities: major_number. minor_number.
 *
 * 0 . 13 (Windows Server 2008)
 * 1 . 1  (Windows 7)
 * 2 . 4  (Windows 8)
 * 3 . 0  (Windows 8 R2)
 * 4 . 0  (Windows 10)
 * 5 . 0  (Newer Windows 10)
 */

#define VERSION_WS2008  ((0 << 16) | (13))
#define VERSION_WIN7    ((1 << 16) | (1))
#define VERSION_WIN8    ((2 << 16) | (4))
#define VERSION_WIN8_1    ((3 << 16) | (0))
#define VERSION_WIN10	((4 << 16) | (0))
#define VERSION_WIN10_V5 ((5 << 16) | (0))

#define VERSION_INVAL -1

#define VERSION_CURRENT VERSION_WIN10_V5

/* Make maximum size of pipe payload of 16K */
#define MAX_PIPE_DATA_PAYLOAD		(sizeof(u8) * 16384)

/* Define PipeMode values. */
#define VMBUS_PIPE_TYPE_BYTE		0x00000000
#define VMBUS_PIPE_TYPE_MESSAGE		0x00000004

/* The size of the user defined data buffer for non-pipe offers. */
#define MAX_USER_DEFINED_BYTES		120

/* The size of the user defined data buffer for pipe offers. */
#define MAX_PIPE_USER_DEFINED_BYTES	116

/*
 * At the center of the Channel Management library is the Channel Offer. This
 * struct contains the fundamental information about an offer.
 */
struct vmbus_channel_offer {
	guid_t if_type;
	guid_t if_instance;

	/*
	 * These two fields are not currently used.
	 */
	u64 reserved1;
	u64 reserved2;

	u16 chn_flags;
	u16 mmio_megabytes;		/* in bytes * 1024 * 1024 */

	union {
		/* Non-pipes: The user has MAX_USER_DEFINED_BYTES bytes. */
		struct {
			unsigned char user_def[MAX_USER_DEFINED_BYTES];
		} std;

		/*
		 * Pipes:
		 * The following sructure is an integrated pipe protocol, which
		 * is implemented on top of standard user-defined data. Pipe
		 * clients have MAX_PIPE_USER_DEFINED_BYTES left for their own
		 * use.
		 */
		struct {
			u32  pipe_mode;
			unsigned char user_def[MAX_PIPE_USER_DEFINED_BYTES];
		} pipe;
	} u;
	/*
	 * The sub_channel_index is defined in win8.
	 */
	u16 sub_channel_index;
	u16 reserved3;
} __packed;

/* Server Flags */
#define VMBUS_CHANNEL_ENUMERATE_DEVICE_INTERFACE	1
#define VMBUS_CHANNEL_SERVER_SUPPORTS_TRANSFER_PAGES	2
#define VMBUS_CHANNEL_SERVER_SUPPORTS_GPADLS		4
#define VMBUS_CHANNEL_NAMED_PIPE_MODE			0x10
#define VMBUS_CHANNEL_LOOPBACK_OFFER			0x100
#define VMBUS_CHANNEL_PARENT_OFFER			0x200
#define VMBUS_CHANNEL_REQUEST_MONITORED_NOTIFICATION	0x400
#define VMBUS_CHANNEL_TLNPI_PROVIDER_OFFER		0x2000

struct vmpacket_descriptor {
	u16 type;
	u16 offset8;
	u16 len8;
	u16 flags;
	u64 trans_id;
} __packed;

struct vmpacket_header {
	u32 prev_pkt_start_offset;
	struct vmpacket_descriptor descriptor;
} __packed;

struct vmtransfer_page_range {
	u32 byte_count;
	u32 byte_offset;
} __packed;

struct vmtransfer_page_packet_header {
	struct vmpacket_descriptor d;
	u16 xfer_pageset_id;
	u8  sender_owns_set;
	u8 reserved;
	u32 range_cnt;
	struct vmtransfer_page_range ranges[1];
} __packed;

struct vmgpadl_packet_header {
	struct vmpacket_descriptor d;
	u32 gpadl;
	u32 reserved;
} __packed;

struct vmadd_remove_transfer_page_set {
	struct vmpacket_descriptor d;
	u32 gpadl;
	u16 xfer_pageset_id;
	u16 reserved;
} __packed;

/*
 * This structure defines a range in guest physical space that can be made to
 * look virtually contiguous.
 */
struct gpa_range {
	u32 byte_count;
	u32 byte_offset;
	u64 pfn_array[0];
};

/*
 * This is the format for an Establish Gpadl packet, which contains a handle by
 * which this GPADL will be known and a set of GPA ranges associated with it.
 * This can be converted to a MDL by the guest OS.  If there are multiple GPA
 * ranges, then the resulting MDL will be "chained," representing multiple VA
 * ranges.
 */
struct vmestablish_gpadl {
	struct vmpacket_descriptor d;
	u32 gpadl;
	u32 range_cnt;
	struct gpa_range range[1];
} __packed;

/*
 * This is the format for a Teardown Gpadl packet, which indicates that the
 * GPADL handle in the Establish Gpadl packet will never be referenced again.
 */
struct vmteardown_gpadl {
	struct vmpacket_descriptor d;
	u32 gpadl;
	u32 reserved;	/* for alignment to a 8-byte boundary */
} __packed;

/*
 * This is the format for a GPA-Direct packet, which contains a set of GPA
 * ranges, in addition to commands and/or data.
 */
struct vmdata_gpa_direct {
	struct vmpacket_descriptor d;
	u32 reserved;
	u32 range_cnt;
	struct gpa_range range[1];
} __packed;

/* This is the format for a Additional Data Packet. */
struct vmadditional_data {
	struct vmpacket_descriptor d;
	u64 total_bytes;
	u32 offset;
	u32 byte_cnt;
	unsigned char data[1];
} __packed;

union vmpacket_largest_possible_header {
	struct vmpacket_descriptor simple_hdr;
	struct vmtransfer_page_packet_header xfer_page_hdr;
	struct vmgpadl_packet_header gpadl_hdr;
	struct vmadd_remove_transfer_page_set add_rm_xfer_page_hdr;
	struct vmestablish_gpadl establish_gpadl_hdr;
	struct vmteardown_gpadl teardown_gpadl_hdr;
	struct vmdata_gpa_direct data_gpa_direct_hdr;
};

#define VMPACKET_DATA_START_ADDRESS(__packet)	\
	(void *)(((unsigned char *)__packet) +	\
	 ((struct vmpacket_descriptor)__packet)->offset8 * 8)

#define VMPACKET_DATA_LENGTH(__packet)		\
	((((struct vmpacket_descriptor)__packet)->len8 -	\
	  ((struct vmpacket_descriptor)__packet)->offset8) * 8)

#define VMPACKET_TRANSFER_MODE(__packet)	\
	(((struct IMPACT)__packet)->type)

enum vmbus_packet_type {
	VM_PKT_INVALID				= 0x0,
	VM_PKT_SYNCH				= 0x1,
	VM_PKT_ADD_XFER_PAGESET			= 0x2,
	VM_PKT_RM_XFER_PAGESET			= 0x3,
	VM_PKT_ESTABLISH_GPADL			= 0x4,
	VM_PKT_TEARDOWN_GPADL			= 0x5,
	VM_PKT_DATA_INBAND			= 0x6,
	VM_PKT_DATA_USING_XFER_PAGES		= 0x7,
	VM_PKT_DATA_USING_GPADL			= 0x8,
	VM_PKT_DATA_USING_GPA_DIRECT		= 0x9,
	VM_PKT_CANCEL_REQUEST			= 0xa,
	VM_PKT_COMP				= 0xb,
	VM_PKT_DATA_USING_ADDITIONAL_PKT	= 0xc,
	VM_PKT_ADDITIONAL_DATA			= 0xd
};

#define VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED	1


/* Version 1 messages */
enum vmbus_channel_message_type {
	CHANNELMSG_INVALID			=  0,
	CHANNELMSG_OFFERCHANNEL		=  1,
	CHANNELMSG_RESCIND_CHANNELOFFER	=  2,
	CHANNELMSG_REQUESTOFFERS		=  3,
	CHANNELMSG_ALLOFFERS_DELIVERED	=  4,
	CHANNELMSG_OPENCHANNEL		=  5,
	CHANNELMSG_OPENCHANNEL_RESULT		=  6,
	CHANNELMSG_CLOSECHANNEL		=  7,
	CHANNELMSG_GPADL_HEADER		=  8,
	CHANNELMSG_GPADL_BODY			=  9,
	CHANNELMSG_GPADL_CREATED		= 10,
	CHANNELMSG_GPADL_TEARDOWN		= 11,
	CHANNELMSG_GPADL_TORNDOWN		= 12,
	CHANNELMSG_RELID_RELEASED		= 13,
	CHANNELMSG_INITIATE_CONTACT		= 14,
	CHANNELMSG_VERSION_RESPONSE		= 15,
	CHANNELMSG_UNLOAD			= 16,
	CHANNELMSG_UNLOAD_RESPONSE		= 17,
	CHANNELMSG_18				= 18,
	CHANNELMSG_19				= 19,
	CHANNELMSG_20				= 20,
	CHANNELMSG_TL_CONNECT_REQUEST		= 21,
	CHANNELMSG_COUNT
};

struct vmbus_channel_message_header {
	enum vmbus_channel_message_type msgtype;
	u32 padding;
} __packed;

/* Query VMBus Version parameters */
struct vmbus_channel_query_vmbus_version {
	struct vmbus_channel_message_header header;
	u32 version;
} __packed;

/* VMBus Version Supported parameters */
struct vmbus_channel_version_supported {
	struct vmbus_channel_message_header header;
	u8 version_supported;
} __packed;

/* Offer Channel parameters */
struct vmbus_channel_offer_channel {
	struct vmbus_channel_message_header header;
	struct vmbus_channel_offer offer;
	u32 child_relid;
	u8 monitorid;
	/*
	 * win7 and beyond splits this field into a bit field.
	 */
	u8 monitor_allocated:1;
	u8 reserved:7;
	/*
	 * These are new fields added in win7 and later.
	 * Do not access these fields without checking the
	 * negotiated protocol.
	 *
	 * If "is_dedicated_interrupt" is set, we must not set the
	 * associated bit in the channel bitmap while sending the
	 * interrupt to the host.
	 *
	 * connection_id is to be used in signaling the host.
	 */
	u16 is_dedicated_interrupt:1;
	u16 reserved1:15;
	u32 connection_id;
} __packed;

/* Rescind Offer parameters */
struct vmbus_channel_rescind_offer {
	struct vmbus_channel_message_header header;
	u32 child_relid;
} __packed;

static inline u32
hv_ringbuffer_pending_size(const struct hv_ring_buffer_info *rbi)
{
	return rbi->ring_buffer->pending_send_sz;
}

/*
 * Request Offer -- no parameters, SynIC message contains the partition ID
 * Set Snoop -- no parameters, SynIC message contains the partition ID
 * Clear Snoop -- no parameters, SynIC message contains the partition ID
 * All Offers Delivered -- no parameters, SynIC message contains the partition
 *		           ID
 * Flush Client -- no parameters, SynIC message contains the partition ID
 */

/* Open Channel parameters */
struct vmbus_channel_open_channel {
	struct vmbus_channel_message_header header;

	/* Identifies the specific VMBus channel that is being opened. */
	u32 child_relid;

	/* ID making a particular open request at a channel offer unique. */
	u32 openid;

	/* GPADL for the channel's ring buffer. */
	u32 ringbuffer_gpadlhandle;

	/*
	 * Starting with win8, this field will be used to specify
	 * the target virtual processor on which to deliver the interrupt for
	 * the host to guest communication.
	 * Prior to win8, incoming channel interrupts would only
	 * be delivered on cpu 0. Setting this value to 0 would
	 * preserve the earlier behavior.
	 */
	u32 target_vp;

	/*
	 * The upstream ring buffer begins at offset zero in the memory
	 * described by RingBufferGpadlHandle. The downstream ring buffer
	 * follows it at this offset (in pages).
	 */
	u32 downstream_ringbuffer_pageoffset;

	/* User-specific data to be passed along to the server endpoint. */
	unsigned char userdata[MAX_USER_DEFINED_BYTES];
} __packed;

/* Open Channel Result parameters */
struct vmbus_channel_open_result {
	struct vmbus_channel_message_header header;
	u32 child_relid;
	u32 openid;
	u32 status;
} __packed;

/* Close channel parameters; */
struct vmbus_channel_close_channel {
	struct vmbus_channel_message_header header;
	u32 child_relid;
} __packed;

/* Channel Message GPADL */
#define GPADL_TYPE_RING_BUFFER		1
#define GPADL_TYPE_SERVER_SAVE_AREA	2
#define GPADL_TYPE_TRANSACTION		8

/*
 * The number of PFNs in a GPADL message is defined by the number of
 * pages that would be spanned by ByteCount and ByteOffset.  If the
 * implied number of PFNs won't fit in this packet, there will be a
 * follow-up packet that contains more.
 */
struct vmbus_channel_gpadl_header {
	struct vmbus_channel_message_header header;
	u32 child_relid;
	u32 gpadl;
	u16 range_buflen;
	u16 rangecount;
	struct gpa_range range[0];
} __packed;

/* This is the followup packet that contains more PFNs. */
struct vmbus_channel_gpadl_body {
	struct vmbus_channel_message_header header;
	u32 msgnumber;
	u32 gpadl;
	u64 pfn[0];
} __packed;

struct vmbus_channel_gpadl_created {
	struct vmbus_channel_message_header header;
	u32 child_relid;
	u32 gpadl;
	u32 creation_status;
} __packed;

struct vmbus_channel_gpadl_teardown {
	struct vmbus_channel_message_header header;
	u32 child_relid;
	u32 gpadl;
} __packed;

struct vmbus_channel_gpadl_torndown {
	struct vmbus_channel_message_header header;
	u32 gpadl;
} __packed;

struct vmbus_channel_relid_released {
	struct vmbus_channel_message_header header;
	u32 child_relid;
} __packed;

struct vmbus_channel_initiate_contact {
	struct vmbus_channel_message_header header;
	u32 vmbus_version_requested;
	u32 target_vcpu; /* The VCPU the host should respond to */
	union {
		u64 interrupt_page;
		struct {
			u8	msg_sint;
			u8	padding1[3];
			u32	padding2;
		};
	};
	u64 monitor_page1;
	u64 monitor_page2;
} __packed;

/* Hyper-V socket: guest's connect()-ing to host */
struct vmbus_channel_tl_connect_request {
	struct vmbus_channel_message_header header;
	guid_t guest_endpoint_id;
	guid_t host_service_id;
} __packed;

struct vmbus_channel_version_response {
	struct vmbus_channel_message_header header;
	u8 version_supported;

	u8 connection_state;
	u16 padding;

	/*
	 * On new hosts that support VMBus protocol 5.0, we must use
	 * VMBUS_MESSAGE_CONNECTION_ID_4 for the Initiate Contact Message,
	 * and for subsequent messages, we must use the Message Connection ID
	 * field in the host-returned Version Response Message.
	 *
	 * On old hosts, we should always use VMBUS_MESSAGE_CONNECTION_ID (1).
	 */
	u32 msg_conn_id;
} __packed;

enum vmbus_channel_state {
	CHANNEL_OFFER_STATE,
	CHANNEL_OPENING_STATE,
	CHANNEL_OPEN_STATE,
	CHANNEL_OPENED_STATE,
};

/*
 * Represents each channel msg on the vmbus connection This is a
 * variable-size data structure depending on the msg type itself
 */
struct vmbus_channel_msginfo {
	/* Bookkeeping stuff */
	struct list_head msglistentry;

	/* So far, this is only used to handle gpadl body message */
	struct list_head submsglist;

	/* Synchronize the request/response if needed */
	struct completion  waitevent;
	struct vmbus_channel *waiting_channel;
	union {
		struct vmbus_channel_version_supported version_supported;
		struct vmbus_channel_open_result open_result;
		struct vmbus_channel_gpadl_torndown gpadl_torndown;
		struct vmbus_channel_gpadl_created gpadl_created;
		struct vmbus_channel_version_response version_response;
	} response;

	u32 msgsize;
	/*
	 * The channel message that goes out on the "wire".
	 * It will contain at minimum the VMBUS_CHANNEL_MESSAGE_HEADER header
	 */
	unsigned char msg[0];
};

struct vmbus_close_msg {
	struct vmbus_channel_msginfo info;
	struct vmbus_channel_close_channel msg;
};

/* Define connection identifier type. */
union hv_connection_id {
	u32 asu32;
	struct {
		u32 id:24;
		u32 reserved:8;
	} u;
};

enum hv_numa_policy {
	HV_BALANCED = 0,
	HV_LOCALIZED,
};

enum vmbus_device_type {
	HV_IDE = 0,
	HV_SCSI,
	HV_FC,
	HV_NIC,
	HV_ND,
	HV_PCIE,
	HV_FB,
	HV_KBD,
	HV_MOUSE,
	HV_KVP,
	HV_TS,
	HV_HB,
	HV_SHUTDOWN,
	HV_FCOPY,
	HV_BACKUP,
	HV_DM,
	HV_UNKNOWN,
};

struct vmbus_device {
	u16  dev_type;
	guid_t guid;
	bool perf_device;
};

struct vmbus_channel {
	struct list_head listentry;

	struct hv_device *device_obj;

	enum vmbus_channel_state state;

	struct vmbus_channel_offer_channel offermsg;
	/*
	 * These are based on the OfferMsg.MonitorId.
	 * Save it here for easy access.
	 */
	u8 monitor_grp;
	u8 monitor_bit;

	bool rescind; /* got rescind msg */
	struct completion rescind_event;

	u32 ringbuffer_gpadlhandle;

	/* Allocated memory for ring buffer */
	struct page *ringbuffer_page;
	u32 ringbuffer_pagecount;
	u32 ringbuffer_send_offset;
	struct hv_ring_buffer_info outbound;	/* send to parent */
	struct hv_ring_buffer_info inbound;	/* receive from parent */

	struct vmbus_close_msg close_msg;

	/* Statistics */
	u64	interrupts;	/* Host to Guest interrupts */
	u64	sig_events;	/* Guest to Host events */

	/*
	 * Guest to host interrupts caused by the outbound ring buffer changing
	 * from empty to not empty.
	 */
	u64 intr_out_empty;

	/*
	 * Indicates that a full outbound ring buffer was encountered. The flag
	 * is set to true when a full outbound ring buffer is encountered and
	 * set to false when a write to the outbound ring buffer is completed.
	 */
	bool out_full_flag;

	/* Channel callback's invoked in softirq context */
	struct tasklet_struct callback_event;
	void (*onchannel_callback)(void *context);
	void *channel_callback_context;

	/*
	 * A channel can be marked for one of three modes of reading:
	 *   BATCHED - callback called from taslket and should read
	 *            channel until empty. Interrupts from the host
	 *            are masked while read is in process (default).
	 *   DIRECT - callback called from tasklet (softirq).
	 *   ISR - callback called in interrupt context and must
	 *         invoke its own deferred processing.
	 *         Host interrupts are disabled and must be re-enabled
	 *         when ring is empty.
	 */
	enum hv_callback_mode {
		HV_CALL_BATCHED,
		HV_CALL_DIRECT,
		HV_CALL_ISR
	} callback_mode;

	bool is_dedicated_interrupt;
	u64 sig_event;

	/*
	 * Starting with win8, this field will be used to specify
	 * the target virtual processor on which to deliver the interrupt for
	 * the host to guest communication.
	 * Prior to win8, incoming channel interrupts would only
	 * be delivered on cpu 0. Setting this value to 0 would
	 * preserve the earlier behavior.
	 */
	u32 target_vp;
	/* The corresponding CPUID in the guest */
	u32 target_cpu;
	/*
	 * State to manage the CPU affiliation of channels.
	 */
	struct cpumask alloced_cpus_in_node;
	int numa_node;
	/*
	 * Support for sub-channels. For high performance devices,
	 * it will be useful to have multiple sub-channels to support
	 * a scalable communication infrastructure with the host.
	 * The support for sub-channels is implemented as an extention
	 * to the current infrastructure.
	 * The initial offer is considered the primary channel and this
	 * offer message will indicate if the host supports sub-channels.
	 * The guest is free to ask for sub-channels to be offerred and can
	 * open these sub-channels as a normal "primary" channel. However,
	 * all sub-channels will have the same type and instance guids as the
	 * primary channel. Requests sent on a given channel will result in a
	 * response on the same channel.
	 */

	/*
	 * Sub-channel creation callback. This callback will be called in
	 * process context when a sub-channel offer is received from the host.
	 * The guest can open the sub-channel in the context of this callback.
	 */
	void (*sc_creation_callback)(struct vmbus_channel *new_sc);

	/*
	 * Channel rescind callback. Some channels (the hvsock ones), need to
	 * register a callback which is invoked in vmbus_onoffer_rescind().
	 */
	void (*chn_rescind_callback)(struct vmbus_channel *channel);

	/*
	 * The spinlock to protect the structure. It is being used to protect
	 * test-and-set access to various attributes of the structure as well
	 * as all sc_list operations.
	 */
	spinlock_t lock;
	/*
	 * All Sub-channels of a primary channel are linked here.
	 */
	struct list_head sc_list;
	/*
	 * The primary channel this sub-channel belongs to.
	 * This will be NULL for the primary channel.
	 */
	struct vmbus_channel *primary_channel;
	/*
	 * Support per-channel state for use by vmbus drivers.
	 */
	void *per_channel_state;
	/*
	 * To support per-cpu lookup mapping of relid to channel,
	 * link up channels based on their CPU affinity.
	 */
	struct list_head percpu_list;

	/*
	 * Defer freeing channel until after all cpu's have
	 * gone through grace period.
	 */
	struct rcu_head rcu;

	/*
	 * For sysfs per-channel properties.
	 */
	struct kobject			kobj;

	/*
	 * For performance critical channels (storage, networking
	 * etc,), Hyper-V has a mechanism to enhance the throughput
	 * at the expense of latency:
	 * When the host is to be signaled, we just set a bit in a shared page
	 * and this bit will be inspected by the hypervisor within a certain
	 * window and if the bit is set, the host will be signaled. The window
	 * of time is the monitor latency - currently around 100 usecs. This
	 * mechanism improves throughput by:
	 *
	 * A) Making the host more efficient - each time it wakes up,
	 *    potentially it will process morev number of packets. The
	 *    monitor latency allows a batch to build up.
	 * B) By deferring the hypercall to signal, we will also minimize
	 *    the interrupts.
	 *
	 * Clearly, these optimizations improve throughput at the expense of
	 * latency. Furthermore, since the channel is shared for both
	 * control and data messages, control messages currently suffer
	 * unnecessary latency adversley impacting performance and boot
	 * time. To fix this issue, permit tagging the channel as being
	 * in "low latency" mode. In this mode, we will bypass the monitor
	 * mechanism.
	 */
	bool low_latency;

	/*
	 * NUMA distribution policy:
	 * We support two policies:
	 * 1) Balanced: Here all performance critical channels are
	 *    distributed evenly amongst all the NUMA nodes.
	 *    This policy will be the default policy.
	 * 2) Localized: All channels of a given instance of a
	 *    performance critical service will be assigned CPUs
	 *    within a selected NUMA node.
	 */
	enum hv_numa_policy affinity_policy;

	bool probe_done;

	/*
	 * We must offload the handling of the primary/sub channels
	 * from the single-threaded vmbus_connection.work_queue to
	 * two different workqueue, otherwise we can block
	 * vmbus_connection.work_queue and hang: see vmbus_process_offer().
	 */
	struct work_struct add_channel_work;

	/*
	 * Guest to host interrupts caused by the inbound ring buffer changing
	 * from full to not full while a packet is waiting.
	 */
	u64 intr_in_full;

	/*
	 * The total number of write operations that encountered a full
	 * outbound ring buffer.
	 */
	u64 out_full_total;

	/*
	 * The number of write operations that were the first to encounter a
	 * full outbound ring buffer.
	 */
	u64 out_full_first;
};

static inline bool is_hvsock_channel(const struct vmbus_channel *c)
{
	return !!(c->offermsg.offer.chn_flags &
		  VMBUS_CHANNEL_TLNPI_PROVIDER_OFFER);
}

static inline void set_channel_affinity_state(struct vmbus_channel *c,
					      enum hv_numa_policy policy)
{
	c->affinity_policy = policy;
}

static inline void set_channel_read_mode(struct vmbus_channel *c,
					enum hv_callback_mode mode)
{
	c->callback_mode = mode;
}

static inline void set_per_channel_state(struct vmbus_channel *c, void *s)
{
	c->per_channel_state = s;
}

static inline void *get_per_channel_state(struct vmbus_channel *c)
{
	return c->per_channel_state;
}

static inline void set_channel_pending_send_size(struct vmbus_channel *c,
						 u32 size)
{
	unsigned long flags;

	if (size) {
		spin_lock_irqsave(&c->outbound.ring_lock, flags);
		++c->out_full_total;

		if (!c->out_full_flag) {
			++c->out_full_first;
			c->out_full_flag = true;
		}
		spin_unlock_irqrestore(&c->outbound.ring_lock, flags);
	} else {
		c->out_full_flag = false;
	}

	c->outbound.ring_buffer->pending_send_sz = size;
}

static inline void set_low_latency_mode(struct vmbus_channel *c)
{
	c->low_latency = true;
}

static inline void clear_low_latency_mode(struct vmbus_channel *c)
{
	c->low_latency = false;
}

void vmbus_onmessage(void *context);

int vmbus_request_offers(void);

/*
 * APIs for managing sub-channels.
 */

void vmbus_set_sc_create_callback(struct vmbus_channel *primary_channel,
			void (*sc_cr_cb)(struct vmbus_channel *new_sc));

void vmbus_set_chn_rescind_callback(struct vmbus_channel *channel,
		void (*chn_rescind_cb)(struct vmbus_channel *));

/*
 * Check if sub-channels have already been offerred. This API will be useful
 * when the driver is unloaded after establishing sub-channels. In this case,
 * when the driver is re-loaded, the driver would have to check if the
 * subchannels have already been established before attempting to request
 * the creation of sub-channels.
 * This function returns TRUE to indicate that subchannels have already been
 * created.
 * This function should be invoked after setting the callback function for
 * sub-channel creation.
 */
bool vmbus_are_subchannels_present(struct vmbus_channel *primary);

/* The format must be the same as struct vmdata_gpa_direct */
struct vmbus_channel_packet_page_buffer {
	u16 type;
	u16 dataoffset8;
	u16 length8;
	u16 flags;
	u64 transactionid;
	u32 reserved;
	u32 rangecount;
	struct hv_page_buffer range[MAX_PAGE_BUFFER_COUNT];
} __packed;

/* The format must be the same as struct vmdata_gpa_direct */
struct vmbus_channel_packet_multipage_buffer {
	u16 type;
	u16 dataoffset8;
	u16 length8;
	u16 flags;
	u64 transactionid;
	u32 reserved;
	u32 rangecount;		/* Always 1 in this case */
	struct hv_multipage_buffer range;
} __packed;

/* The format must be the same as struct vmdata_gpa_direct */
struct vmbus_packet_mpb_array {
	u16 type;
	u16 dataoffset8;
	u16 length8;
	u16 flags;
	u64 transactionid;
	u32 reserved;
	u32 rangecount;         /* Always 1 in this case */
	struct hv_mpb_array range;
} __packed;

int vmbus_alloc_ring(struct vmbus_channel *channel,
		     u32 send_size, u32 recv_size);
void vmbus_free_ring(struct vmbus_channel *channel);

int vmbus_connect_ring(struct vmbus_channel *channel,
		       void (*onchannel_callback)(void *context),
		       void *context);
int vmbus_disconnect_ring(struct vmbus_channel *channel);

extern int vmbus_open(struct vmbus_channel *channel,
			    u32 send_ringbuffersize,
			    u32 recv_ringbuffersize,
			    void *userdata,
			    u32 userdatalen,
			    void (*onchannel_callback)(void *context),
			    void *context);

extern void vmbus_close(struct vmbus_channel *channel);

extern int vmbus_sendpacket(struct vmbus_channel *channel,
				  void *buffer,
				  u32 bufferLen,
				  u64 requestid,
				  enum vmbus_packet_type type,
				  u32 flags);

extern int vmbus_sendpacket_pagebuffer(struct vmbus_channel *channel,
					    struct hv_page_buffer pagebuffers[],
					    u32 pagecount,
					    void *buffer,
					    u32 bufferlen,
					    u64 requestid);

extern int vmbus_sendpacket_mpb_desc(struct vmbus_channel *channel,
				     struct vmbus_packet_mpb_array *mpb,
				     u32 desc_size,
				     void *buffer,
				     u32 bufferlen,
				     u64 requestid);

extern int vmbus_establish_gpadl(struct vmbus_channel *channel,
				      void *kbuffer,
				      u32 size,
				      u32 *gpadl_handle);

extern int vmbus_teardown_gpadl(struct vmbus_channel *channel,
				     u32 gpadl_handle);

void vmbus_reset_channel_cb(struct vmbus_channel *channel);

extern int vmbus_recvpacket(struct vmbus_channel *channel,
				  void *buffer,
				  u32 bufferlen,
				  u32 *buffer_actual_len,
				  u64 *requestid);

extern int vmbus_recvpacket_raw(struct vmbus_channel *channel,
				     void *buffer,
				     u32 bufferlen,
				     u32 *buffer_actual_len,
				     u64 *requestid);


extern void vmbus_ontimer(unsigned long data);

/* Base driver object */
struct hv_driver {
	const char *name;

	/*
	 * A hvsock offer, which has a VMBUS_CHANNEL_TLNPI_PROVIDER_OFFER
	 * channel flag, actually doesn't mean a synthetic device because the
	 * offer's if_type/if_instance can change for every new hvsock
	 * connection.
	 *
	 * However, to facilitate the notification of new-offer/rescind-offer
	 * from vmbus driver to hvsock driver, we can handle hvsock offer as
	 * a special vmbus device, and hence we need the below flag to
	 * indicate if the driver is the hvsock driver or not: we need to
	 * specially treat the hvosck offer & driver in vmbus_match().
	 */
	bool hvsock;

	/* the device type supported by this driver */
	guid_t dev_type;
	const struct hv_vmbus_device_id *id_table;

	struct device_driver driver;

	/* dynamic device GUID's */
	struct  {
		spinlock_t lock;
		struct list_head list;
	} dynids;

	int (*probe)(struct hv_device *, const struct hv_vmbus_device_id *);
	int (*remove)(struct hv_device *);
	void (*shutdown)(struct hv_device *);

};

/* Base device object */
struct hv_device {
	/* the device type id of this device */
	guid_t dev_type;

	/* the device instance id of this device */
	guid_t dev_instance;
	u16 vendor_id;
	u16 device_id;

	struct device device;
	char *driver_override; /* Driver name to force a match */

	struct vmbus_channel *channel;
	struct kset	     *channels_kset;
};


static inline struct hv_device *device_to_hv_device(struct device *d)
{
	return container_of(d, struct hv_device, device);
}

static inline struct hv_driver *drv_to_hv_drv(struct device_driver *d)
{
	return container_of(d, struct hv_driver, driver);
}

static inline void hv_set_drvdata(struct hv_device *dev, void *data)
{
	dev_set_drvdata(&dev->device, data);
}

static inline void *hv_get_drvdata(struct hv_device *dev)
{
	return dev_get_drvdata(&dev->device);
}

struct hv_ring_buffer_debug_info {
	u32 current_interrupt_mask;
	u32 current_read_index;
	u32 current_write_index;
	u32 bytes_avail_toread;
	u32 bytes_avail_towrite;
};


int hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
				struct hv_ring_buffer_debug_info *debug_info);

/* Vmbus interface */
#define vmbus_driver_register(driver)	\
	__vmbus_driver_register(driver, THIS_MODULE, KBUILD_MODNAME)
int __must_check __vmbus_driver_register(struct hv_driver *hv_driver,
					 struct module *owner,
					 const char *mod_name);
void vmbus_driver_unregister(struct hv_driver *hv_driver);

void vmbus_hvsock_device_unregister(struct vmbus_channel *channel);

int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
			resource_size_t min, resource_size_t max,
			resource_size_t size, resource_size_t align,
			bool fb_overlap_ok);
void vmbus_free_mmio(resource_size_t start, resource_size_t size);

/*
 * GUID definitions of various offer types - services offered to the guest.
 */

/*
 * Network GUID
 * {f8615163-df3e-46c5-913f-f2d2f965ed0e}
 */
#define HV_NIC_GUID \
	.guid = GUID_INIT(0xf8615163, 0xdf3e, 0x46c5, 0x91, 0x3f, \
			  0xf2, 0xd2, 0xf9, 0x65, 0xed, 0x0e)

/*
 * IDE GUID
 * {32412632-86cb-44a2-9b5c-50d1417354f5}
 */
#define HV_IDE_GUID \
	.guid = GUID_INIT(0x32412632, 0x86cb, 0x44a2, 0x9b, 0x5c, \
			  0x50, 0xd1, 0x41, 0x73, 0x54, 0xf5)

/*
 * SCSI GUID
 * {ba6163d9-04a1-4d29-b605-72e2ffb1dc7f}
 */
#define HV_SCSI_GUID \
	.guid = GUID_INIT(0xba6163d9, 0x04a1, 0x4d29, 0xb6, 0x05, \
			  0x72, 0xe2, 0xff, 0xb1, 0xdc, 0x7f)

/*
 * Shutdown GUID
 * {0e0b6031-5213-4934-818b-38d90ced39db}
 */
#define HV_SHUTDOWN_GUID \
	.guid = GUID_INIT(0x0e0b6031, 0x5213, 0x4934, 0x81, 0x8b, \
			  0x38, 0xd9, 0x0c, 0xed, 0x39, 0xdb)

/*
 * Time Synch GUID
 * {9527E630-D0AE-497b-ADCE-E80AB0175CAF}
 */
#define HV_TS_GUID \
	.guid = GUID_INIT(0x9527e630, 0xd0ae, 0x497b, 0xad, 0xce, \
			  0xe8, 0x0a, 0xb0, 0x17, 0x5c, 0xaf)

/*
 * Heartbeat GUID
 * {57164f39-9115-4e78-ab55-382f3bd5422d}
 */
#define HV_HEART_BEAT_GUID \
	.guid = GUID_INIT(0x57164f39, 0x9115, 0x4e78, 0xab, 0x55, \
			  0x38, 0x2f, 0x3b, 0xd5, 0x42, 0x2d)

/*
 * KVP GUID
 * {a9a0f4e7-5a45-4d96-b827-8a841e8c03e6}
 */
#define HV_KVP_GUID \
	.guid = GUID_INIT(0xa9a0f4e7, 0x5a45, 0x4d96, 0xb8, 0x27, \
			  0x8a, 0x84, 0x1e, 0x8c, 0x03, 0xe6)

/*
 * Dynamic memory GUID
 * {525074dc-8985-46e2-8057-a307dc18a502}
 */
#define HV_DM_GUID \
	.guid = GUID_INIT(0x525074dc, 0x8985, 0x46e2, 0x80, 0x57, \
			  0xa3, 0x07, 0xdc, 0x18, 0xa5, 0x02)

/*
 * Mouse GUID
 * {cfa8b69e-5b4a-4cc0-b98b-8ba1a1f3f95a}
 */
#define HV_MOUSE_GUID \
	.guid = GUID_INIT(0xcfa8b69e, 0x5b4a, 0x4cc0, 0xb9, 0x8b, \
			  0x8b, 0xa1, 0xa1, 0xf3, 0xf9, 0x5a)

/*
 * Keyboard GUID
 * {f912ad6d-2b17-48ea-bd65-f927a61c7684}
 */
#define HV_KBD_GUID \
	.guid = GUID_INIT(0xf912ad6d, 0x2b17, 0x48ea, 0xbd, 0x65, \
			  0xf9, 0x27, 0xa6, 0x1c, 0x76, 0x84)

/*
 * VSS (Backup/Restore) GUID
 */
#define HV_VSS_GUID \
	.guid = GUID_INIT(0x35fa2e29, 0xea23, 0x4236, 0x96, 0xae, \
			  0x3a, 0x6e, 0xba, 0xcb, 0xa4, 0x40)
/*
 * Synthetic Video GUID
 * {DA0A7802-E377-4aac-8E77-0558EB1073F8}
 */
#define HV_SYNTHVID_GUID \
	.guid = GUID_INIT(0xda0a7802, 0xe377, 0x4aac, 0x8e, 0x77, \
			  0x05, 0x58, 0xeb, 0x10, 0x73, 0xf8)

/*
 * Synthetic FC GUID
 * {2f9bcc4a-0069-4af3-b76b-6fd0be528cda}
 */
#define HV_SYNTHFC_GUID \
	.guid = GUID_INIT(0x2f9bcc4a, 0x0069, 0x4af3, 0xb7, 0x6b, \
			  0x6f, 0xd0, 0xbe, 0x52, 0x8c, 0xda)

/*
 * Guest File Copy Service
 * {34D14BE3-DEE4-41c8-9AE7-6B174977C192}
 */

#define HV_FCOPY_GUID \
	.guid = GUID_INIT(0x34d14be3, 0xdee4, 0x41c8, 0x9a, 0xe7, \
			  0x6b, 0x17, 0x49, 0x77, 0xc1, 0x92)

/*
 * NetworkDirect. This is the guest RDMA service.
 * {8c2eaf3d-32a7-4b09-ab99-bd1f1c86b501}
 */
#define HV_ND_GUID \
	.guid = GUID_INIT(0x8c2eaf3d, 0x32a7, 0x4b09, 0xab, 0x99, \
			  0xbd, 0x1f, 0x1c, 0x86, 0xb5, 0x01)

/*
 * PCI Express Pass Through
 * {44C4F61D-4444-4400-9D52-802E27EDE19F}
 */

#define HV_PCIE_GUID \
	.guid = GUID_INIT(0x44c4f61d, 0x4444, 0x4400, 0x9d, 0x52, \
			  0x80, 0x2e, 0x27, 0xed, 0xe1, 0x9f)

/*
 * Linux doesn't support the 3 devices: the first two are for
 * Automatic Virtual Machine Activation, and the third is for
 * Remote Desktop Virtualization.
 * {f8e65716-3cb3-4a06-9a60-1889c5cccab5}
 * {3375baf4-9e15-4b30-b765-67acb10d607b}
 * {276aacf4-ac15-426c-98dd-7521ad3f01fe}
 */

#define HV_AVMA1_GUID \
	.guid = GUID_INIT(0xf8e65716, 0x3cb3, 0x4a06, 0x9a, 0x60, \
			  0x18, 0x89, 0xc5, 0xcc, 0xca, 0xb5)

#define HV_AVMA2_GUID \
	.guid = GUID_INIT(0x3375baf4, 0x9e15, 0x4b30, 0xb7, 0x65, \
			  0x67, 0xac, 0xb1, 0x0d, 0x60, 0x7b)

#define HV_RDV_GUID \
	.guid = GUID_INIT(0x276aacf4, 0xac15, 0x426c, 0x98, 0xdd, \
			  0x75, 0x21, 0xad, 0x3f, 0x01, 0xfe)

/*
 * Common header for Hyper-V ICs
 */

#define ICMSGTYPE_NEGOTIATE		0
#define ICMSGTYPE_HEARTBEAT		1
#define ICMSGTYPE_KVPEXCHANGE		2
#define ICMSGTYPE_SHUTDOWN		3
#define ICMSGTYPE_TIMESYNC		4
#define ICMSGTYPE_VSS			5

#define ICMSGHDRFLAG_TRANSACTION	1
#define ICMSGHDRFLAG_REQUEST		2
#define ICMSGHDRFLAG_RESPONSE		4


/*
 * While we want to handle util services as regular devices,
 * there is only one instance of each of these services; so
 * we statically allocate the service specific state.
 */

struct hv_util_service {
	u8 *recv_buffer;
	void *channel;
	void (*util_cb)(void *);
	int (*util_init)(struct hv_util_service *);
	void (*util_deinit)(void);
};

struct vmbuspipe_hdr {
	u32 flags;
	u32 msgsize;
} __packed;

struct ic_version {
	u16 major;
	u16 minor;
} __packed;

struct icmsg_hdr {
	struct ic_version icverframe;
	u16 icmsgtype;
	struct ic_version icvermsg;
	u16 icmsgsize;
	u32 status;
	u8 ictransaction_id;
	u8 icflags;
	u8 reserved[2];
} __packed;

struct icmsg_negotiate {
	u16 icframe_vercnt;
	u16 icmsg_vercnt;
	u32 reserved;
	struct ic_version icversion_data[1]; /* any size array */
} __packed;

struct shutdown_msg_data {
	u32 reason_code;
	u32 timeout_seconds;
	u32 flags;
	u8  display_message[2048];
} __packed;

struct heartbeat_msg_data {
	u64 seq_num;
	u32 reserved[8];
} __packed;

/* Time Sync IC defs */
#define ICTIMESYNCFLAG_PROBE	0
#define ICTIMESYNCFLAG_SYNC	1
#define ICTIMESYNCFLAG_SAMPLE	2

#ifdef __x86_64__
#define WLTIMEDELTA	116444736000000000L	/* in 100ns unit */
#else
#define WLTIMEDELTA	116444736000000000LL
#endif

struct ictimesync_data {
	u64 parenttime;
	u64 childtime;
	u64 roundtriptime;
	u8 flags;
} __packed;

struct ictimesync_ref_data {
	u64 parenttime;
	u64 vmreferencetime;
	u8 flags;
	char leapflags;
	char stratum;
	u8 reserved[3];
} __packed;

struct hyperv_service_callback {
	u8 msg_type;
	char *log_msg;
	guid_t data;
	struct vmbus_channel *channel;
	void (*callback)(void *context);
};

#define MAX_SRV_VER	0x7ffffff
extern bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp, u8 *buf,
				const int *fw_version, int fw_vercnt,
				const int *srv_version, int srv_vercnt,
				int *nego_fw_version, int *nego_srv_version);

void hv_process_channel_removal(struct vmbus_channel *channel);

void vmbus_setevent(struct vmbus_channel *channel);
/*
 * Negotiated version with the Host.
 */

extern __u32 vmbus_proto_version;

int vmbus_send_tl_connect_request(const guid_t *shv_guest_servie_id,
				  const guid_t *shv_host_servie_id);
void vmbus_set_event(struct vmbus_channel *channel);

/* Get the start of the ring buffer. */
static inline void *
hv_get_ring_buffer(const struct hv_ring_buffer_info *ring_info)
{
	return ring_info->ring_buffer->buffer;
}

/*
 * Mask off host interrupt callback notifications
 */
static inline void hv_begin_read(struct hv_ring_buffer_info *rbi)
{
	rbi->ring_buffer->interrupt_mask = 1;

	/* make sure mask update is not reordered */
	virt_mb();
}

/*
 * Re-enable host callback and return number of outstanding bytes
 */
static inline u32 hv_end_read(struct hv_ring_buffer_info *rbi)
{

	rbi->ring_buffer->interrupt_mask = 0;

	/* make sure mask update is not reordered */
	virt_mb();

	/*
	 * Now check to see if the ring buffer is still empty.
	 * If it is not, we raced and we need to process new
	 * incoming messages.
	 */
	return hv_get_bytes_to_read(rbi);
}

/*
 * An API to support in-place processing of incoming VMBUS packets.
 */

/* Get data payload associated with descriptor */
static inline void *hv_pkt_data(const struct vmpacket_descriptor *desc)
{
	return (void *)((unsigned long)desc + (desc->offset8 << 3));
}

/* Get data size associated with descriptor */
static inline u32 hv_pkt_datalen(const struct vmpacket_descriptor *desc)
{
	return (desc->len8 << 3) - (desc->offset8 << 3);
}


struct vmpacket_descriptor *
hv_pkt_iter_first(struct vmbus_channel *channel);

struct vmpacket_descriptor *
__hv_pkt_iter_next(struct vmbus_channel *channel,
		   const struct vmpacket_descriptor *pkt);

void hv_pkt_iter_close(struct vmbus_channel *channel);

/*
 * Get next packet descriptor from iterator
 * If at end of list, return NULL and update host.
 */
static inline struct vmpacket_descriptor *
hv_pkt_iter_next(struct vmbus_channel *channel,
		 const struct vmpacket_descriptor *pkt)
{
	struct vmpacket_descriptor *nxt;

	nxt = __hv_pkt_iter_next(channel, pkt);
	if (!nxt)
		hv_pkt_iter_close(channel);

	return nxt;
}

#define foreach_vmbus_pkt(pkt, channel) \
	for (pkt = hv_pkt_iter_first(channel); pkt; \
	    pkt = hv_pkt_iter_next(channel, pkt))

#endif /* _HYPERV_H */