1 /* 2 * Memory Device Interface 3 * 4 * Copyright (c) 2018 Red Hat, Inc. 5 * 6 * Authors: 7 * David Hildenbrand <david@redhat.com> 8 * 9 * This work is licensed under the terms of the GNU GPL, version 2 or later. 10 * See the COPYING file in the top-level directory. 11 */ 12 13 #ifndef MEMORY_DEVICE_H 14 #define MEMORY_DEVICE_H 15 16 #include "hw/qdev-core.h" 17 #include "qapi/qapi-types-machine.h" 18 #include "qom/object.h" 19 20 #define TYPE_MEMORY_DEVICE "memory-device" 21 22 typedef struct MemoryDeviceClass MemoryDeviceClass; 23 DECLARE_CLASS_CHECKERS(MemoryDeviceClass, MEMORY_DEVICE, 24 TYPE_MEMORY_DEVICE) 25 #define MEMORY_DEVICE(obj) \ 26 INTERFACE_CHECK(MemoryDeviceState, (obj), TYPE_MEMORY_DEVICE) 27 28 typedef struct MemoryDeviceState MemoryDeviceState; 29 30 /** 31 * MemoryDeviceClass: 32 * 33 * All memory devices need to implement TYPE_MEMORY_DEVICE as an interface. 34 * 35 * A memory device is a device that owns a memory region which is 36 * mapped into guest physical address space at a certain address. The 37 * address in guest physical memory can either be specified explicitly 38 * or get assigned automatically. 39 * 40 * Some memory device might not own a memory region in certain device 41 * configurations. Such devices can logically get (un)plugged, however, 42 * empty memory devices are mostly ignored by the memory device code. 43 * 44 * Conceptually, memory devices only span one memory region. If multiple 45 * successive memory regions are used, a covering memory region has to 46 * be provided. Scattered memory regions are not supported for single 47 * devices. 48 * 49 * The device memory region returned via @get_memory_region may either be a 50 * single RAM memory region or a memory region container with subregions 51 * that are RAM memory regions or aliases to RAM memory regions. Other 52 * memory regions or subregions are not supported. 53 * 54 * If the device memory region returned via @get_memory_region is a 55 * memory region container, it's supported to dynamically (un)map subregions 56 * as long as the number of memslots returned by @get_memslots() won't 57 * be exceeded and as long as all memory regions are of the same kind (e.g., 58 * all RAM or all ROM). 59 */ 60 struct MemoryDeviceClass { 61 /* private */ 62 InterfaceClass parent_class; 63 64 /* 65 * Return the address of the memory device in guest physical memory. 66 * 67 * Called when (un)plugging a memory device or when iterating over 68 * all memory devices mapped into guest physical address space. 69 * 70 * If "0" is returned, no address has been specified by the user and 71 * no address has been assigned to this memory device yet. 72 */ 73 uint64_t (*get_addr)(const MemoryDeviceState *md); 74 75 /* 76 * Set the address of the memory device in guest physical memory. 77 * 78 * Called when plugging the memory device to configure the determined 79 * address in guest physical memory. 80 */ 81 void (*set_addr)(MemoryDeviceState *md, uint64_t addr, Error **errp); 82 83 /* 84 * Return the amount of memory provided by the memory device currently 85 * usable ("plugged") by the VM. 86 * 87 * Called when calculating the total amount of ram available to the 88 * VM (e.g. to report memory stats to the user). 89 * 90 * This is helpful for devices that dynamically manage the amount of 91 * memory accessible by the guest via the reserved memory region. For 92 * most devices, this corresponds to the size of the memory region. 93 */ 94 uint64_t (*get_plugged_size)(const MemoryDeviceState *md, Error **errp); 95 96 /* 97 * Return the memory region of the memory device. If the device is 98 * completely empty, returns NULL without an error. 99 * 100 * Called when (un)plugging the memory device, to (un)map the 101 * memory region in guest physical memory, but also to detect the 102 * required alignment during address assignment or when the size of the 103 * memory region is required. 104 */ 105 MemoryRegion *(*get_memory_region)(MemoryDeviceState *md, Error **errp); 106 107 /* 108 * Optional: Instruct the memory device to decide how many memory slots 109 * it requires, not exceeding the given limit. 110 * 111 * Called exactly once when pre-plugging the memory device, before 112 * querying the number of memslots using @get_memslots the first time. 113 */ 114 void (*decide_memslots)(MemoryDeviceState *md, unsigned int limit); 115 116 /* 117 * Optional for memory devices that require only a single memslot, 118 * required for all other memory devices: Return the number of memslots 119 * (distinct RAM memory regions in the device memory region) that are 120 * required by the device. 121 * 122 * If this function is not implemented, the assumption is "1". 123 * 124 * Called when (un)plugging the memory device, to check if the requirements 125 * can be satisfied, and to do proper accounting. 126 */ 127 unsigned int (*get_memslots)(MemoryDeviceState *md); 128 129 /* 130 * Optional: Return the desired minimum alignment of the device in guest 131 * physical address space. The final alignment is computed based on this 132 * alignment and the alignment requirements of the memory region. 133 * 134 * Called when plugging the memory device to detect the required alignment 135 * during address assignment. 136 */ 137 uint64_t (*get_min_alignment)(const MemoryDeviceState *md); 138 139 /* 140 * Translate the memory device into #MemoryDeviceInfo. 141 */ 142 void (*fill_device_info)(const MemoryDeviceState *md, 143 MemoryDeviceInfo *info); 144 }; 145 146 /* 147 * Traditionally, KVM/vhost in many setups supported 509 memslots, whereby 148 * 253 memslots were "reserved" for boot memory and other devices (such 149 * as PCI BARs, which can get mapped dynamically) and 256 memslots were 150 * dedicated for DIMMs. These magic numbers worked reliably in the past. 151 * 152 * Further, using many memslots can negatively affect performance, so setting 153 * the soft-limit of memslots used by memory devices to the traditional 154 * DIMM limit of 256 sounds reasonable. 155 * 156 * If we have less than 509 memslots, we will instruct memory devices that 157 * support automatically deciding how many memslots to use to only use a single 158 * one. 159 * 160 * Hotplugging vhost devices with at least 509 memslots is not expected to 161 * cause problems, not even when devices automatically decided how many memslots 162 * to use. 163 */ 164 #define MEMORY_DEVICES_SOFT_MEMSLOT_LIMIT 256 165 #define MEMORY_DEVICES_SAFE_MAX_MEMSLOTS 509 166 167 MemoryDeviceInfoList *qmp_memory_device_list(void); 168 uint64_t get_plugged_memory_size(void); 169 unsigned int memory_devices_get_reserved_memslots(void); 170 bool memory_devices_memslot_auto_decision_active(void); 171 void memory_device_pre_plug(MemoryDeviceState *md, MachineState *ms, 172 Error **errp); 173 void memory_device_plug(MemoryDeviceState *md, MachineState *ms); 174 void memory_device_unplug(MemoryDeviceState *md, MachineState *ms); 175 uint64_t memory_device_get_region_size(const MemoryDeviceState *md, 176 Error **errp); 177 178 #endif 179