| 1 | /* |
| 2 | * QEMU host POSIX shared memory object backend |
| 3 | * |
| 4 | * Copyright (C) 2024 Red Hat Inc |
| 5 | * |
| 6 | * Authors: |
| 7 | * Stefano Garzarella <sgarzare@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 | #include "qemu/osdep.h" |
| 14 | #include "system/hostmem.h" |
| 15 | #include "qapi/error.h" |
| 16 | #include "migration/cpr.h" |
| 17 | |
| 18 | #define TYPE_MEMORY_BACKEND_SHM "memory-backend-shm" |
| 19 | |
| 20 | OBJECT_DECLARE_SIMPLE_TYPE(HostMemoryBackendShm, MEMORY_BACKEND_SHM) |
| 21 | |
| 22 | struct HostMemoryBackendShm { |
| 23 | HostMemoryBackend parent_obj; |
| 24 | }; |
| 25 | |
| 26 | static bool |
| 27 | shm_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) |
| 28 | { |
| 29 | g_autofree char *backend_name = host_memory_backend_get_name(backend); |
| 30 | uint32_t ram_flags; |
| 31 | int fd = cpr_find_fd(backend_name, 0); |
| 32 | |
| 33 | if (!backend->size) { |
| 34 | error_setg(errp, "can't create shm backend with size 0"); |
| 35 | return false; |
| 36 | } |
| 37 | |
| 38 | if (!backend->share) { |
| 39 | error_setg(errp, "can't create shm backend with `share=off`"); |
| 40 | return false; |
| 41 | } |
| 42 | |
| 43 | if (fd >= 0) { |
| 44 | goto have_fd; |
| 45 | } |
| 46 | |
| 47 | fd = qemu_shm_alloc(backend->size, errp); |
| 48 | if (fd < 0) { |
| 49 | return false; |
| 50 | } |
| 51 | cpr_save_fd(backend_name, 0, fd); |
| 52 | |
| 53 | have_fd: |
| 54 | /* Let's do the same as memory-backend-ram,share=on would do. */ |
| 55 | ram_flags = RAM_SHARED; |
| 56 | ram_flags |= backend->reserve ? 0 : RAM_NORESERVE; |
| 57 | ram_flags |= backend->guest_memfd ? RAM_GUEST_MEMFD : 0; |
| 58 | |
| 59 | return memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend), |
| 60 | backend_name, backend->size, |
| 61 | ram_flags, fd, 0, errp); |
| 62 | } |
| 63 | |
| 64 | static void |
| 65 | shm_backend_instance_init(Object *obj) |
| 66 | { |
| 67 | HostMemoryBackendShm *m = MEMORY_BACKEND_SHM(obj); |
| 68 | |
| 69 | MEMORY_BACKEND(m)->share = true; |
| 70 | } |
| 71 | |
| 72 | static void |
| 73 | shm_backend_class_init(ObjectClass *oc, const void *data) |
| 74 | { |
| 75 | HostMemoryBackendClass *bc = MEMORY_BACKEND_CLASS(oc); |
| 76 | |
| 77 | bc->alloc = shm_backend_memory_alloc; |
| 78 | } |
| 79 | |
| 80 | static const TypeInfo shm_backend_info = { |
| 81 | .name = TYPE_MEMORY_BACKEND_SHM, |
| 82 | .parent = TYPE_MEMORY_BACKEND, |
| 83 | .instance_init = shm_backend_instance_init, |
| 84 | .class_init = shm_backend_class_init, |
| 85 | .instance_size = sizeof(HostMemoryBackendShm), |
| 86 | }; |
| 87 | |
| 88 | static void register_types(void) |
| 89 | { |
| 90 | type_register_static(&shm_backend_info); |
| 91 | } |
| 92 | |
| 93 | type_init(register_types); |