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/* SPDX-License-Identifier: BSD-3-Clause */
/*
* Virtio Mem Device
*
* Copyright Red Hat, Inc. 2020
*
* Authors:
* David Hildenbrand <david@redhat.com>
*
* 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.
*/
#ifndef _LINUX_VIRTIO_MEM_H
#define _LINUX_VIRTIO_MEM_H
#include <linux/types.h>
#include <linux/virtio_types.h>
#include <linux/virtio_ids.h>
#include <linux/virtio_config.h>
/*
* Each virtio-mem device manages a dedicated region in physical address
* space. Each device can belong to a single NUMA node, multiple devices
* for a single NUMA node are possible. A virtio-mem device is like a
* "resizable DIMM" consisting of small memory blocks that can be plugged
* or unplugged. The device driver is responsible for (un)plugging memory
* blocks on demand.
*
* Virtio-mem devices can only operate on their assigned memory region in
* order to (un)plug memory. A device cannot (un)plug memory belonging to
* other devices.
*
* The "region_size" corresponds to the maximum amount of memory that can
* be provided by a device. The "size" corresponds to the amount of memory
* that is currently plugged. "requested_size" corresponds to a request
* from the device to the device driver to (un)plug blocks. The
* device driver should try to (un)plug blocks in order to reach the
* "requested_size". It is impossible to plug more memory than requested.
*
* The "usable_region_size" represents the memory region that can actually
* be used to (un)plug memory. It is always at least as big as the
* "requested_size" and will grow dynamically. It will only shrink when
* explicitly triggered (VIRTIO_MEM_REQ_UNPLUG).
*
* There are no guarantees what will happen if unplugged memory is
* read/written. In general, unplugged memory should not be touched, because
* the resulting action is undefined. There is one exception: without
* VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE, unplugged memory inside the usable
* region can be read, to simplify creation of memory dumps.
*
* It can happen that the device cannot process a request, because it is
* busy. The device driver has to retry later.
*
* Usually, during system resets all memory will get unplugged, so the
* device driver can start with a clean state. However, in specific
* scenarios (if the device is busy) it can happen that the device still
* has memory plugged. The device driver can request to unplug all memory
* (VIRTIO_MEM_REQ_UNPLUG) - which might take a while to succeed if the
* device is busy.
*/
/* --- virtio-mem: feature bits --- */
/* node_id is an ACPI PXM and is valid */
#define VIRTIO_MEM_F_ACPI_PXM 0
/* unplugged memory must not be accessed */
#define VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE 1
/* --- virtio-mem: guest -> host requests --- */
/* request to plug memory blocks */
#define VIRTIO_MEM_REQ_PLUG 0
/* request to unplug memory blocks */
#define VIRTIO_MEM_REQ_UNPLUG 1
/* request to unplug all blocks and shrink the usable size */
#define VIRTIO_MEM_REQ_UNPLUG_ALL 2
/* request information about the plugged state of memory blocks */
#define VIRTIO_MEM_REQ_STATE 3
struct virtio_mem_req_plug {
__virtio64 addr;
__virtio16 nb_blocks;
__virtio16 padding[3];
};
struct virtio_mem_req_unplug {
__virtio64 addr;
__virtio16 nb_blocks;
__virtio16 padding[3];
};
struct virtio_mem_req_state {
__virtio64 addr;
__virtio16 nb_blocks;
__virtio16 padding[3];
};
struct virtio_mem_req {
__virtio16 type;
__virtio16 padding[3];
union {
struct virtio_mem_req_plug plug;
struct virtio_mem_req_unplug unplug;
struct virtio_mem_req_state state;
} u;
};
/* --- virtio-mem: host -> guest response --- */
/*
* Request processed successfully, applicable for
* - VIRTIO_MEM_REQ_PLUG
* - VIRTIO_MEM_REQ_UNPLUG
* - VIRTIO_MEM_REQ_UNPLUG_ALL
* - VIRTIO_MEM_REQ_STATE
*/
#define VIRTIO_MEM_RESP_ACK 0
/*
* Request denied - e.g. trying to plug more than requested, applicable for
* - VIRTIO_MEM_REQ_PLUG
*/
#define VIRTIO_MEM_RESP_NACK 1
/*
* Request cannot be processed right now, try again later, applicable for
* - VIRTIO_MEM_REQ_PLUG
* - VIRTIO_MEM_REQ_UNPLUG
* - VIRTIO_MEM_REQ_UNPLUG_ALL
*/
#define VIRTIO_MEM_RESP_BUSY 2
/*
* Error in request (e.g. addresses/alignment), applicable for
* - VIRTIO_MEM_REQ_PLUG
* - VIRTIO_MEM_REQ_UNPLUG
* - VIRTIO_MEM_REQ_STATE
*/
#define VIRTIO_MEM_RESP_ERROR 3
/* State of memory blocks is "plugged" */
#define VIRTIO_MEM_STATE_PLUGGED 0
/* State of memory blocks is "unplugged" */
#define VIRTIO_MEM_STATE_UNPLUGGED 1
/* State of memory blocks is "mixed" */
#define VIRTIO_MEM_STATE_MIXED 2
struct virtio_mem_resp_state {
__virtio16 state;
};
struct virtio_mem_resp {
__virtio16 type;
__virtio16 padding[3];
union {
struct virtio_mem_resp_state state;
} u;
};
/* --- virtio-mem: configuration --- */
struct virtio_mem_config {
/* Block size and alignment. Cannot change. */
__le64 block_size;
/* Valid with VIRTIO_MEM_F_ACPI_PXM. Cannot change. */
__le16 node_id;
__u8 padding[6];
/* Start address of the memory region. Cannot change. */
__le64 addr;
/* Region size (maximum). Cannot change. */
__le64 region_size;
/*
* Currently usable region size. Can grow up to region_size. Can
* shrink due to VIRTIO_MEM_REQ_UNPLUG_ALL (in which case no config
* update will be sent).
*/
__le64 usable_region_size;
/*
* Currently used size. Changes due to plug/unplug requests, but no
* config updates will be sent.
*/
__le64 plugged_size;
/* Requested size. New plug requests cannot exceed it. Can change. */
__le64 requested_size;
};
#endif /* _LINUX_VIRTIO_MEM_H */
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