include/standard-headers/linux/virtio_mem.h

   1 /* SPDX-License-Identifier: BSD-3-Clause */
   2 /*
   3  * Virtio Mem Device
   4  *
   5  * Copyright Red Hat, Inc. 2020
   6  *
   7  * Authors:
   8  *     David Hildenbrand <david@redhat.com>
   9  *
  10  * This header is BSD licensed so anyone can use the definitions
  11  * to implement compatible drivers/servers:
  12  *
  13  * Redistribution and use in source and binary forms, with or without
  14  * modification, are permitted provided that the following conditions
  15  * are met:
  16  * 1. Redistributions of source code must retain the above copyright
  17  *    notice, this list of conditions and the following disclaimer.
  18  * 2. Redistributions in binary form must reproduce the above copyright
  19  *    notice, this list of conditions and the following disclaimer in the
  20  *    documentation and/or other materials provided with the distribution.
  21  * 3. Neither the name of IBM nor the names of its contributors
  22  *    may be used to endorse or promote products derived from this software
  23  *    without specific prior written permission.
  24  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  25  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  26  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  27  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL IBM OR
  28  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  29  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  30  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  31  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  32  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  33  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  34  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  35  * SUCH DAMAGE.
  36  */
  37
  38 #ifndef _LINUX_VIRTIO_MEM_H
  39 #define _LINUX_VIRTIO_MEM_H
  40
  41 #include "standard-headers/linux/types.h"
  42 #include "standard-headers/linux/virtio_types.h"
  43 #include "standard-headers/linux/virtio_ids.h"
  44 #include "standard-headers/linux/virtio_config.h"
  45
  46 /*
  47  * Each virtio-mem device manages a dedicated region in physical address
  48  * space. Each device can belong to a single NUMA node, multiple devices
  49  * for a single NUMA node are possible. A virtio-mem device is like a
  50  * "resizable DIMM" consisting of small memory blocks that can be plugged
  51  * or unplugged. The device driver is responsible for (un)plugging memory
  52  * blocks on demand.
  53  *
  54  * Virtio-mem devices can only operate on their assigned memory region in
  55  * order to (un)plug memory. A device cannot (un)plug memory belonging to
  56  * other devices.
  57  *
  58  * The "region_size" corresponds to the maximum amount of memory that can
  59  * be provided by a device. The "size" corresponds to the amount of memory
  60  * that is currently plugged. "requested_size" corresponds to a request
  61  * from the device to the device driver to (un)plug blocks. The
  62  * device driver should try to (un)plug blocks in order to reach the
  63  * "requested_size". It is impossible to plug more memory than requested.
  64  *
  65  * The "usable_region_size" represents the memory region that can actually
  66  * be used to (un)plug memory. It is always at least as big as the
  67  * "requested_size" and will grow dynamically. It will only shrink when
  68  * explicitly triggered (VIRTIO_MEM_REQ_UNPLUG).
  69  *
  70  * There are no guarantees what will happen if unplugged memory is
  71  * read/written. In general, unplugged memory should not be touched, because
  72  * the resulting action is undefined. There is one exception: without
  73  * VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE, unplugged memory inside the usable
  74  * region can be read, to simplify creation of memory dumps.
  75  *
  76  * It can happen that the device cannot process a request, because it is
  77  * busy. The device driver has to retry later.
  78  *
  79  * Usually, during system resets all memory will get unplugged, so the
  80  * device driver can start with a clean state. However, in specific
  81  * scenarios (if the device is busy) it can happen that the device still
  82  * has memory plugged. The device driver can request to unplug all memory
  83  * (VIRTIO_MEM_REQ_UNPLUG) - which might take a while to succeed if the
  84  * device is busy.
  85  */
  86
  87 /* --- virtio-mem: feature bits --- */
  88
  89 /* node_id is an ACPI PXM and is valid */
  90 #define VIRTIO_MEM_F_ACPI_PXM           0
  91 /* unplugged memory must not be accessed */
  92 #define VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE     1
  93
  94
  95 /* --- virtio-mem: guest -> host requests --- */
  96
  97 /* request to plug memory blocks */
  98 #define VIRTIO_MEM_REQ_PLUG                     0
  99 /* request to unplug memory blocks */
 100 #define VIRTIO_MEM_REQ_UNPLUG                   1
 101 /* request to unplug all blocks and shrink the usable size */
 102 #define VIRTIO_MEM_REQ_UNPLUG_ALL               2
 103 /* request information about the plugged state of memory blocks */
 104 #define VIRTIO_MEM_REQ_STATE                    3
 105
 106 struct virtio_mem_req_plug {
 107         __virtio64 addr;
 108         __virtio16 nb_blocks;
 109         __virtio16 padding[3];
 110 };
 111
 112 struct virtio_mem_req_unplug {
 113         __virtio64 addr;
 114         __virtio16 nb_blocks;
 115         __virtio16 padding[3];
 116 };
 117
 118 struct virtio_mem_req_state {
 119         __virtio64 addr;
 120         __virtio16 nb_blocks;
 121         __virtio16 padding[3];
 122 };
 123
 124 struct virtio_mem_req {
 125         __virtio16 type;
 126         __virtio16 padding[3];
 127
 128         union {
 129                 struct virtio_mem_req_plug plug;
 130                 struct virtio_mem_req_unplug unplug;
 131                 struct virtio_mem_req_state state;
 132         } u;
 133 };
 134
 135
 136 /* --- virtio-mem: host -> guest response --- */
 137
 138 /*
 139  * Request processed successfully, applicable for
 140  * - VIRTIO_MEM_REQ_PLUG
 141  * - VIRTIO_MEM_REQ_UNPLUG
 142  * - VIRTIO_MEM_REQ_UNPLUG_ALL
 143  * - VIRTIO_MEM_REQ_STATE
 144  */
 145 #define VIRTIO_MEM_RESP_ACK                     0
 146 /*
 147  * Request denied - e.g. trying to plug more than requested, applicable for
 148  * - VIRTIO_MEM_REQ_PLUG
 149  */
 150 #define VIRTIO_MEM_RESP_NACK                    1
 151 /*
 152  * Request cannot be processed right now, try again later, applicable for
 153  * - VIRTIO_MEM_REQ_PLUG
 154  * - VIRTIO_MEM_REQ_UNPLUG
 155  * - VIRTIO_MEM_REQ_UNPLUG_ALL
 156  */
 157 #define VIRTIO_MEM_RESP_BUSY                    2
 158 /*
 159  * Error in request (e.g. addresses/alignment), applicable for
 160  * - VIRTIO_MEM_REQ_PLUG
 161  * - VIRTIO_MEM_REQ_UNPLUG
 162  * - VIRTIO_MEM_REQ_STATE
 163  */
 164 #define VIRTIO_MEM_RESP_ERROR                   3
 165
 166
 167 /* State of memory blocks is "plugged" */
 168 #define VIRTIO_MEM_STATE_PLUGGED                0
 169 /* State of memory blocks is "unplugged" */
 170 #define VIRTIO_MEM_STATE_UNPLUGGED              1
 171 /* State of memory blocks is "mixed" */
 172 #define VIRTIO_MEM_STATE_MIXED                  2
 173
 174 struct virtio_mem_resp_state {
 175         __virtio16 state;
 176 };
 177
 178 struct virtio_mem_resp {
 179         __virtio16 type;
 180         __virtio16 padding[3];
 181
 182         union {
 183                 struct virtio_mem_resp_state state;
 184         } u;
 185 };
 186
 187 /* --- virtio-mem: configuration --- */
 188
 189 struct virtio_mem_config {
 190         /* Block size and alignment. Cannot change. */
 191         uint64_t block_size;
 192         /* Valid with VIRTIO_MEM_F_ACPI_PXM. Cannot change. */
 193         uint16_t node_id;
 194         uint8_t padding[6];
 195         /* Start address of the memory region. Cannot change. */
 196         uint64_t addr;
 197         /* Region size (maximum). Cannot change. */
 198         uint64_t region_size;
 199         /*
 200          * Currently usable region size. Can grow up to region_size. Can
 201          * shrink due to VIRTIO_MEM_REQ_UNPLUG_ALL (in which case no config
 202          * update will be sent).
 203          */
 204         uint64_t usable_region_size;
 205         /*
 206          * Currently used size. Changes due to plug/unplug requests, but no
 207          * config updates will be sent.
 208          */
 209         uint64_t plugged_size;
 210         /* Requested size. New plug requests cannot exceed it. Can change. */
 211         uint64_t requested_size;
 212 };
 213
 214 #endif /* _LINUX_VIRTIO_MEM_H */