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       1                 :            : #ifndef _UAPI_LINUX_VIRTIO_RING_H
       2                 :            : #define _UAPI_LINUX_VIRTIO_RING_H
       3                 :            : /* An interface for efficient virtio implementation, currently for use by KVM,
       4                 :            :  * but hopefully others soon.  Do NOT change this since it will
       5                 :            :  * break existing servers and clients.
       6                 :            :  *
       7                 :            :  * This header is BSD licensed so anyone can use the definitions to implement
       8                 :            :  * compatible drivers/servers.
       9                 :            :  *
      10                 :            :  * Redistribution and use in source and binary forms, with or without
      11                 :            :  * modification, are permitted provided that the following conditions
      12                 :            :  * are met:
      13                 :            :  * 1. Redistributions of source code must retain the above copyright
      14                 :            :  *    notice, this list of conditions and the following disclaimer.
      15                 :            :  * 2. Redistributions in binary form must reproduce the above copyright
      16                 :            :  *    notice, this list of conditions and the following disclaimer in the
      17                 :            :  *    documentation and/or other materials provided with the distribution.
      18                 :            :  * 3. Neither the name of IBM nor the names of its contributors
      19                 :            :  *    may be used to endorse or promote products derived from this software
      20                 :            :  *    without specific prior written permission.
      21                 :            :  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND
      22                 :            :  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
      23                 :            :  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
      24                 :            :  * ARE DISCLAIMED.  IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
      25                 :            :  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
      26                 :            :  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
      27                 :            :  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
      28                 :            :  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
      29                 :            :  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
      30                 :            :  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
      31                 :            :  * SUCH DAMAGE.
      32                 :            :  *
      33                 :            :  * Copyright Rusty Russell IBM Corporation 2007. */
      34                 :            : #ifndef __KERNEL__
      35                 :            : #include <stdint.h>
      36                 :            : #endif
      37                 :            : #include <linux/types.h>
      38                 :            : #include <linux/virtio_types.h>
      39                 :            : 
      40                 :            : /* This marks a buffer as continuing via the next field. */
      41                 :            : #define VRING_DESC_F_NEXT       1
      42                 :            : /* This marks a buffer as write-only (otherwise read-only). */
      43                 :            : #define VRING_DESC_F_WRITE      2
      44                 :            : /* This means the buffer contains a list of buffer descriptors. */
      45                 :            : #define VRING_DESC_F_INDIRECT   4
      46                 :            : 
      47                 :            : /*
      48                 :            :  * Mark a descriptor as available or used in packed ring.
      49                 :            :  * Notice: they are defined as shifts instead of shifted values.
      50                 :            :  */
      51                 :            : #define VRING_PACKED_DESC_F_AVAIL       7
      52                 :            : #define VRING_PACKED_DESC_F_USED        15
      53                 :            : 
      54                 :            : /* The Host uses this in used->flags to advise the Guest: don't kick me when
      55                 :            :  * you add a buffer.  It's unreliable, so it's simply an optimization.  Guest
      56                 :            :  * will still kick if it's out of buffers. */
      57                 :            : #define VRING_USED_F_NO_NOTIFY  1
      58                 :            : /* The Guest uses this in avail->flags to advise the Host: don't interrupt me
      59                 :            :  * when you consume a buffer.  It's unreliable, so it's simply an
      60                 :            :  * optimization.  */
      61                 :            : #define VRING_AVAIL_F_NO_INTERRUPT      1
      62                 :            : 
      63                 :            : /* Enable events in packed ring. */
      64                 :            : #define VRING_PACKED_EVENT_FLAG_ENABLE  0x0
      65                 :            : /* Disable events in packed ring. */
      66                 :            : #define VRING_PACKED_EVENT_FLAG_DISABLE 0x1
      67                 :            : /*
      68                 :            :  * Enable events for a specific descriptor in packed ring.
      69                 :            :  * (as specified by Descriptor Ring Change Event Offset/Wrap Counter).
      70                 :            :  * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated.
      71                 :            :  */
      72                 :            : #define VRING_PACKED_EVENT_FLAG_DESC    0x2
      73                 :            : 
      74                 :            : /*
      75                 :            :  * Wrap counter bit shift in event suppression structure
      76                 :            :  * of packed ring.
      77                 :            :  */
      78                 :            : #define VRING_PACKED_EVENT_F_WRAP_CTR   15
      79                 :            : 
      80                 :            : /* We support indirect buffer descriptors */
      81                 :            : #define VIRTIO_RING_F_INDIRECT_DESC     28
      82                 :            : 
      83                 :            : /* The Guest publishes the used index for which it expects an interrupt
      84                 :            :  * at the end of the avail ring. Host should ignore the avail->flags field. */
      85                 :            : /* The Host publishes the avail index for which it expects a kick
      86                 :            :  * at the end of the used ring. Guest should ignore the used->flags field. */
      87                 :            : #define VIRTIO_RING_F_EVENT_IDX         29
      88                 :            : 
      89                 :            : /* Virtio ring descriptors: 16 bytes.  These can chain together via "next". */
      90                 :            : struct vring_desc {
      91                 :            :         /* Address (guest-physical). */
      92                 :            :         __virtio64 addr;
      93                 :            :         /* Length. */
      94                 :            :         __virtio32 len;
      95                 :            :         /* The flags as indicated above. */
      96                 :            :         __virtio16 flags;
      97                 :            :         /* We chain unused descriptors via this, too */
      98                 :            :         __virtio16 next;
      99                 :            : };
     100                 :            : 
     101                 :            : struct vring_avail {
     102                 :            :         __virtio16 flags;
     103                 :            :         __virtio16 idx;
     104                 :            :         __virtio16 ring[];
     105                 :            : };
     106                 :            : 
     107                 :            : /* u32 is used here for ids for padding reasons. */
     108                 :            : struct vring_used_elem {
     109                 :            :         /* Index of start of used descriptor chain. */
     110                 :            :         __virtio32 id;
     111                 :            :         /* Total length of the descriptor chain which was used (written to) */
     112                 :            :         __virtio32 len;
     113                 :            : };
     114                 :            : 
     115                 :            : struct vring_used {
     116                 :            :         __virtio16 flags;
     117                 :            :         __virtio16 idx;
     118                 :            :         struct vring_used_elem ring[];
     119                 :            : };
     120                 :            : 
     121                 :            : struct vring {
     122                 :            :         unsigned int num;
     123                 :            : 
     124                 :            :         struct vring_desc *desc;
     125                 :            : 
     126                 :            :         struct vring_avail *avail;
     127                 :            : 
     128                 :            :         struct vring_used *used;
     129                 :            : };
     130                 :            : 
     131                 :            : /* Alignment requirements for vring elements.
     132                 :            :  * When using pre-virtio 1.0 layout, these fall out naturally.
     133                 :            :  */
     134                 :            : #define VRING_AVAIL_ALIGN_SIZE 2
     135                 :            : #define VRING_USED_ALIGN_SIZE 4
     136                 :            : #define VRING_DESC_ALIGN_SIZE 16
     137                 :            : 
     138                 :            : /* The standard layout for the ring is a continuous chunk of memory which looks
     139                 :            :  * like this.  We assume num is a power of 2.
     140                 :            :  *
     141                 :            :  * struct vring
     142                 :            :  * {
     143                 :            :  *      // The actual descriptors (16 bytes each)
     144                 :            :  *      struct vring_desc desc[num];
     145                 :            :  *
     146                 :            :  *      // A ring of available descriptor heads with free-running index.
     147                 :            :  *      __virtio16 avail_flags;
     148                 :            :  *      __virtio16 avail_idx;
     149                 :            :  *      __virtio16 available[num];
     150                 :            :  *      __virtio16 used_event_idx;
     151                 :            :  *
     152                 :            :  *      // Padding to the next align boundary.
     153                 :            :  *      char pad[];
     154                 :            :  *
     155                 :            :  *      // A ring of used descriptor heads with free-running index.
     156                 :            :  *      __virtio16 used_flags;
     157                 :            :  *      __virtio16 used_idx;
     158                 :            :  *      struct vring_used_elem used[num];
     159                 :            :  *      __virtio16 avail_event_idx;
     160                 :            :  * };
     161                 :            :  */
     162                 :            : /* We publish the used event index at the end of the available ring, and vice
     163                 :            :  * versa. They are at the end for backwards compatibility. */
     164                 :            : #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
     165                 :            : #define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num])
     166                 :            : 
     167                 :          0 : static inline void vring_init(struct vring *vr, unsigned int num, void *p,
     168                 :            :                               unsigned long align)
     169                 :            : {
     170                 :          0 :         vr->num = num;
     171                 :          0 :         vr->desc = p;
     172                 :          0 :         vr->avail = (struct vring_avail *)((char *)p + num * sizeof(struct vring_desc));
     173                 :          0 :         vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] + sizeof(__virtio16)
     174                 :          0 :                 + align-1) & ~(align - 1));
     175                 :            : }
     176                 :            : 
     177                 :          0 : static inline unsigned vring_size(unsigned int num, unsigned long align)
     178                 :            : {
     179                 :          0 :         return ((sizeof(struct vring_desc) * num + sizeof(__virtio16) * (3 + num)
     180                 :          0 :                  + align - 1) & ~(align - 1))
     181         [ #  # ]:          0 :                 + sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num;
     182                 :            : }
     183                 :            : 
     184                 :            : /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */
     185                 :            : /* Assuming a given event_idx value from the other side, if
     186                 :            :  * we have just incremented index from old to new_idx,
     187                 :            :  * should we trigger an event? */
     188                 :          0 : static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old)
     189                 :            : {
     190                 :            :         /* Note: Xen has similar logic for notification hold-off
     191                 :            :          * in include/xen/interface/io/ring.h with req_event and req_prod
     192                 :            :          * corresponding to event_idx + 1 and new_idx respectively.
     193                 :            :          * Note also that req_event and req_prod in Xen start at 1,
     194                 :            :          * event indexes in virtio start at 0. */
     195                 :          0 :         return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);
     196                 :            : }
     197                 :            : 
     198                 :            : struct vring_packed_desc_event {
     199                 :            :         /* Descriptor Ring Change Event Offset/Wrap Counter. */
     200                 :            :         __le16 off_wrap;
     201                 :            :         /* Descriptor Ring Change Event Flags. */
     202                 :            :         __le16 flags;
     203                 :            : };
     204                 :            : 
     205                 :            : struct vring_packed_desc {
     206                 :            :         /* Buffer Address. */
     207                 :            :         __le64 addr;
     208                 :            :         /* Buffer Length. */
     209                 :            :         __le32 len;
     210                 :            :         /* Buffer ID. */
     211                 :            :         __le16 id;
     212                 :            :         /* The flags depending on descriptor type. */
     213                 :            :         __le16 flags;
     214                 :            : };
     215                 :            : 
     216                 :            : #endif /* _UAPI_LINUX_VIRTIO_RING_H */