#ifndef _LINUX_VIRTIO_BALLOON_H
  #define _LINUX_VIRTIO_BALLOON_H

  /* This header is BSD licensed so anyone can use the definitions to implement

   * compatible drivers/servers.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the name of IBM nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE. */

  #include <linux/types.h>

  #include <linux/virtio_types.h>

  #include <linux/virtio_ids.h>

  #include <linux/virtio_config.h>

  /* The feature bitmap for virtio balloon */
  #define VIRTIO_BALLOON_F_MUST_TELL_HOST	0 /* Tell before reclaiming pages */

  #define VIRTIO_BALLOON_F_STATS_VQ	1 /* Memory Stats virtqueue */

  #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon on OOM */

  /* Size of a PFN in the balloon interface. */
  #define VIRTIO_BALLOON_PFN_SHIFT 12

  struct virtio_balloon_config {

  	/* Number of pages host wants Guest to give up. */

  	__u32 num_pages;

  	/* Number of pages we've actually got in balloon. */

  	__u32 actual;

  };

  
  #define VIRTIO_BALLOON_S_SWAP_IN  0   /* Amount of memory swapped in */
  #define VIRTIO_BALLOON_S_SWAP_OUT 1   /* Amount of memory swapped out */
  #define VIRTIO_BALLOON_S_MAJFLT   2   /* Number of major faults */
  #define VIRTIO_BALLOON_S_MINFLT   3   /* Number of minor faults */
  #define VIRTIO_BALLOON_S_MEMFREE  4   /* Total amount of free memory */
  #define VIRTIO_BALLOON_S_MEMTOT   5   /* Total amount of memory */

  #define VIRTIO_BALLOON_S_AVAIL    6   /* Available memory as in /proc */
  #define VIRTIO_BALLOON_S_NR       7

  /*
   * Memory statistics structure.
   * Driver fills an array of these structures and passes to device.
   *
   * NOTE: fields are laid out in a way that would make compiler add padding
   * between and after fields, so we have to use compiler-specific attributes to
   * pack it, to disable this padding. This also often causes compiler to
   * generate suboptimal code.
   *
   * We maintain this statistics structure format for backwards compatibility,
   * but don't follow this example.
   *
   * If implementing a similar structure, do something like the below instead:
   *     struct virtio_balloon_stat {
   *         __virtio16 tag;
   *         __u8 reserved[6];
   *         __virtio64 val;
   *     };
   *
   * In other words, add explicit reserved fields to align field and
   * structure boundaries at field size, avoiding compiler padding
   * without the packed attribute.
   */

  struct virtio_balloon_stat {

  	__virtio16 tag;
  	__virtio64 val;

  } __attribute__((packed));

  #endif /* _LINUX_VIRTIO_BALLOON_H */