    /******************************************************************************
     * Argo : Hypervisor-Mediated data eXchange
     *
     * Derived from v4v, the version 2 of v2v.
     *
     * Copyright (c) 2010, Citrix Systems
     * Copyright (c) 2018-2019, BAE Systems
     *
     * Permission is hereby granted, free of charge, to any person obtaining a copy
     * of this software and associated documentation files (the "Software"), to
     * deal in the Software without restriction, including without limitation the
     * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
     * sell copies of the Software, and to permit persons to whom the Software is
     * furnished to do so, subject to the following conditions:
     *
     * The above copyright notice and this permission notice shall be included in
     * all copies or substantial portions of the Software.
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
     * DEALINGS IN THE SOFTWARE.
     *
     */

    #ifndef __XEN_PUBLIC_ARGO_H__
    #define __XEN_PUBLIC_ARGO_H__

    #include "xen.h"

    #define XEN_ARGO_DOMID_ANY       DOMID_INVALID

    /* The maximum size of an Argo ring is defined to be: 16MB (0x1000000 bytes). */
    #define XEN_ARGO_MAX_RING_SIZE  (0x1000000ULL)

    /* Fixed-width type for "argo port" number. Nothing to do with evtchns. */
    typedef uint32_t xen_argo_port_t;

    /* gfn type: 64-bit fixed-width on all architectures */
    typedef uint64_t xen_argo_gfn_t;

    /*
     * XEN_ARGO_MAXIOV : maximum number of iovs accepted in a single sendv.
     * Caution is required if this value is increased: this determines the size of
     * an array of xen_argo_iov_t structs on the hypervisor stack, so could cause
     * stack overflow if the value is too large.
     * The Linux Argo driver never passes more than two iovs.
    */
    #define XEN_ARGO_MAXIOV          8U

    typedef struct xen_argo_iov
    {
        XEN_GUEST_HANDLE(uint8) iov_hnd;
        uint32_t iov_len;
        uint32_t pad;
    } xen_argo_iov_t;

    typedef struct xen_argo_addr
    {
        xen_argo_port_t aport;
        domid_t domain_id;
        uint16_t pad;
    } xen_argo_addr_t;

    typedef struct xen_argo_send_addr
    {
        xen_argo_addr_t src;
        xen_argo_addr_t dst;
    } xen_argo_send_addr_t;

    typedef struct xen_argo_ring
    {
        /* Guests should use atomic operations to access rx_ptr */
        uint32_t rx_ptr;
        /* Guests should use atomic operations to access tx_ptr */
        uint32_t tx_ptr;
        /*
         * Header space reserved for later use. Align the start of the ring to a
         * multiple of the message slot size.
         */
        uint8_t reserved[56];
        uint8_t ring[XEN_FLEX_ARRAY_DIM];
    } xen_argo_ring_t;

    typedef struct xen_argo_register_ring
    {
        xen_argo_port_t aport;
        domid_t partner_id;
        uint16_t pad;
        uint32_t len;
    } xen_argo_register_ring_t;

    typedef struct xen_argo_unregister_ring
    {
        xen_argo_port_t aport;
        domid_t partner_id;
        uint16_t pad;
    } xen_argo_unregister_ring_t;

    /* Messages on the ring are padded to a multiple of this size. */
    #define XEN_ARGO_MSG_SLOT_SIZE 0x10

    /*
     * Notify flags
     */
    /* Ring exists */
    #define XEN_ARGO_RING_EXISTS            (1U << 0)
    /* Ring is shared, not unicast */
    #define XEN_ARGO_RING_SHARED            (1U << 1)
    /* Ring is empty */
    #define XEN_ARGO_RING_EMPTY             (1U << 2)
    /* Sufficient space to queue space_required bytes might exist */
    #define XEN_ARGO_RING_SUFFICIENT        (1U << 3)
    /* Insufficient ring size for space_required bytes */
    #define XEN_ARGO_RING_EMSGSIZE          (1U << 4)
    /* Too many domains waiting for available space signals for this ring */
    #define XEN_ARGO_RING_EBUSY             (1U << 5)

    typedef struct xen_argo_ring_data_ent
    {
        xen_argo_addr_t ring;
        uint16_t flags;
        uint16_t pad;
        uint32_t space_required;
        uint32_t max_message_size;
    } xen_argo_ring_data_ent_t;

    typedef struct xen_argo_ring_data
    {
        uint32_t nent;
        uint32_t pad;
        xen_argo_ring_data_ent_t data[XEN_FLEX_ARRAY_DIM];
    } xen_argo_ring_data_t;

    struct xen_argo_ring_message_header
    {
        uint32_t len;
        xen_argo_addr_t source;
        uint32_t message_type;
        uint8_t data[XEN_FLEX_ARRAY_DIM];
    };

    /*
     * Hypercall operations
     */

    /*
     * XEN_ARGO_OP_register_ring
     *
     * Register a ring using the guest-supplied memory pages.
     * Also used to reregister an existing ring (eg. after resume from hibernate).
     *
     * The first argument struct indicates the port number for the ring to register
     * and the partner domain, if any, that is to be allowed to send to the ring.
     * A wildcard (XEN_ARGO_DOMID_ANY) may be supplied instead of a partner domid,
     * and if the hypervisor has wildcard sender rings enabled, this will allow
     * any domain (XSM notwithstanding) to send to the ring.
     *
     * The second argument is an array of guest frame numbers and the third argument
     * indicates the size of the array. This operation only supports 4K-sized pages.
     *
     * arg1: XEN_GUEST_HANDLE(xen_argo_register_ring_t)
     * arg2: XEN_GUEST_HANDLE(xen_argo_gfn_t)
     * arg3: unsigned long npages
     * arg4: unsigned long flags (32-bit value)
     */
    #define XEN_ARGO_OP_register_ring     1

    /* Register op flags */
    /*
     * Fail exist:
     * If set, reject attempts to (re)register an existing established ring.
     * If clear, reregistration occurs if the ring exists, with the new ring
     * taking the place of the old, preserving tx_ptr if it remains valid.
     */
    #define XEN_ARGO_REGISTER_FLAG_FAIL_EXIST  0x1

    #ifdef __XEN__
    /* Mask for all defined flags. */
    #define XEN_ARGO_REGISTER_FLAG_MASK XEN_ARGO_REGISTER_FLAG_FAIL_EXIST
    #endif

    /*
     * XEN_ARGO_OP_unregister_ring
     *
     * Unregister a previously-registered ring, ending communication.
     *
     * arg1: XEN_GUEST_HANDLE(xen_argo_unregister_ring_t)
     * arg2: NULL
     * arg3: 0 (ZERO)
     * arg4: 0 (ZERO)
     */
    #define XEN_ARGO_OP_unregister_ring     2

    /*
     * XEN_ARGO_OP_sendv
     *
     * Send a list of buffers contained in iovs.
     *
     * The send address struct specifies the source and destination addresses
     * for the message being sent, which are used to find the destination ring:
     * Xen first looks for a most-specific match with a registered ring with
     *  (id.addr == dst) and (id.partner == sending_domain) ;
     * if that fails, it then looks for a wildcard match (aka multicast receiver)
     * where (id.addr == dst) and (id.partner == DOMID_ANY).
     *
     * For each iov entry, send iov_len bytes from iov_base to the destination ring.
     * If insufficient space exists in the destination ring, it will return -EAGAIN
     * and Xen will notify the caller when sufficient space becomes available.
     *
     * The message type is a 32-bit data field available to communicate message
     * context data (eg. kernel-to-kernel, rather than application layer).
     *
     * arg1: XEN_GUEST_HANDLE(xen_argo_send_addr_t) source and dest addresses
     * arg2: XEN_GUEST_HANDLE(xen_argo_iov_t) iovs
     * arg3: unsigned long niov
     * arg4: unsigned long message type (32-bit value)
     */
    #define XEN_ARGO_OP_sendv               3

    /*
     * XEN_ARGO_OP_notify
     *
     * Asks Xen for information about other rings in the system.
     *
     * ent->ring is the xen_argo_addr_t of the ring you want information on.
     * Uses the same ring matching rules as XEN_ARGO_OP_sendv.
     *
     * ent->space_required : if this field is not null then Xen will check
     * that there is space in the destination ring for this many bytes of payload.
     * If the ring is too small for the requested space_required, it will set the
     * XEN_ARGO_RING_EMSGSIZE flag on return.
     * If sufficient space is available, it will set XEN_ARGO_RING_SUFFICIENT
     * and CANCEL any pending notification for that ent->ring; otherwise it
     * will schedule a notification event and the flag will not be set.
     *
     * These flags are set by Xen when notify replies:
     * XEN_ARGO_RING_EXISTS     ring exists
     * XEN_ARGO_RING_SHARED     ring is registered for wildcard partner
     * XEN_ARGO_RING_EMPTY      ring is empty
     * XEN_ARGO_RING_SUFFICIENT sufficient space for space_required is there
     * XEN_ARGO_RING_EMSGSIZE   space_required is too large for the ring size
     * XEN_ARGO_RING_EBUSY      too many domains waiting for available space signals
     *
     * arg1: XEN_GUEST_HANDLE(xen_argo_ring_data_t) ring_data (may be NULL)
     * arg2: NULL
     * arg3: 0 (ZERO)
     * arg4: 0 (ZERO)
     */
    #define XEN_ARGO_OP_notify              4

    #endif