On Tue, Nov 11, 2025 at 10:10:52AM +0100, Albert Esteve wrote: > Add SHMEM_MAP/UNMAP requests to vhost-user for dynamic management of > VIRTIO Shared Memory mappings. > > This implementation introduces VirtioSharedMemoryMapping as a unified > QOM object that manages both the mapping metadata and MemoryRegion > lifecycle. This object provides reference-counted lifecycle management > with automatic cleanup of file descriptors and memory regions > through QOM finalization. > > This request allows backends to dynamically map file descriptors into a > VIRTIO Shared Memory Region identified by their shmid. Maps are created > using memory_region_init_ram_from_fd() with configurable read/write > permissions, and the resulting MemoryRegions are added as subregions to > the shmem container region. The mapped memory is then advertised to the > guest VIRTIO drivers as a base address plus offset for reading and > writting according to the requested mmap flags. > > The backend can unmap memory ranges within a given VIRTIO Shared Memory > Region to free resources. Upon receiving this message, the frontend > removes the MemoryRegion as a subregion and automatically unreferences > the VirtioSharedMemoryMapping object, triggering cleanup if no other > references exist. > > Error handling has been improved to ensure consistent behavior across > handlers that manage their own vhost_user_send_resp() calls. Since > these handlers clear the VHOST_USER_NEED_REPLY_MASK flag, explicit > error checking ensures proper connection closure on failures, > maintaining the expected error flow. > > Note the memory region commit for these operations needs to be delayed > until after we reply to the backend to avoid deadlocks. Otherwise, > the MemoryListener would send a VHOST_USER_SET_MEM_TABLE message > before the reply. > > Reviewed-by: Stefan Hajnoczi <[email protected]> > Signed-off-by: Albert Esteve <[email protected]>
breaks windows build: https://gitlab.com/mstredhat/qemu/-/jobs/12974866673 ./hw/virtio/virtio.c: In function 'virtio_shared_memory_mapping_new': ../hw/virtio/virtio.c:3209:10: error: implicit declaration of function 'memory_region_init_ram_from_fd'; did you mean 'memory_region_init_ram_ptr'? [-Wimplicit-function-declaration] 3209 | if (!memory_region_init_ram_from_fd(mr, OBJECT(mapping), mr_name->str, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | memory_region_init_ram_ptr ../hw/virtio/virtio.c:3209:10: error: nested extern declaration of 'memory_region_init_ram_from_fd' [-Werror=nested-externs] cc1: all warnings being treated as errors this needs stubs. > --- > hw/virtio/vhost-user.c | 269 ++++++++++++++++++++++ > hw/virtio/virtio.c | 199 ++++++++++++++++ > include/hw/virtio/virtio.h | 135 +++++++++++ > subprojects/libvhost-user/libvhost-user.c | 70 ++++++ > subprojects/libvhost-user/libvhost-user.h | 54 +++++ > 5 files changed, 727 insertions(+) > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > index 63fa9a1b4b..5706a2bd8a 100644 > --- a/hw/virtio/vhost-user.c > +++ b/hw/virtio/vhost-user.c > @@ -104,6 +104,7 @@ typedef enum VhostUserRequest { > VHOST_USER_GET_SHARED_OBJECT = 41, > VHOST_USER_SET_DEVICE_STATE_FD = 42, > VHOST_USER_CHECK_DEVICE_STATE = 43, > + VHOST_USER_GET_SHMEM_CONFIG = 44, > VHOST_USER_MAX > } VhostUserRequest; > > @@ -115,6 +116,8 @@ typedef enum VhostUserBackendRequest { > VHOST_USER_BACKEND_SHARED_OBJECT_ADD = 6, > VHOST_USER_BACKEND_SHARED_OBJECT_REMOVE = 7, > VHOST_USER_BACKEND_SHARED_OBJECT_LOOKUP = 8, > + VHOST_USER_BACKEND_SHMEM_MAP = 9, > + VHOST_USER_BACKEND_SHMEM_UNMAP = 10, > VHOST_USER_BACKEND_MAX > } VhostUserBackendRequest; > > @@ -136,6 +139,12 @@ typedef struct VhostUserMemRegMsg { > VhostUserMemoryRegion region; > } VhostUserMemRegMsg; > > +typedef struct VhostUserShMemConfig { > + uint32_t nregions; > + uint32_t padding; > + uint64_t memory_sizes[VIRTIO_MAX_SHMEM_REGIONS]; > +} VhostUserShMemConfig; > + > typedef struct VhostUserLog { > uint64_t mmap_size; > uint64_t mmap_offset; > @@ -192,6 +201,23 @@ typedef struct VhostUserShared { > unsigned char uuid[16]; > } VhostUserShared; > > +/* For the flags field of VhostUserMMap */ > +#define VHOST_USER_FLAG_MAP_RW (1u << 0) > + > +typedef struct { > + /* VIRTIO Shared Memory Region ID */ > + uint8_t shmid; > + uint8_t padding[7]; > + /* File offset */ > + uint64_t fd_offset; > + /* Offset within the VIRTIO Shared Memory Region */ > + uint64_t shm_offset; > + /* Size of the mapping */ > + uint64_t len; > + /* Flags for the mmap operation, from VHOST_USER_FLAG_MAP_* */ > + uint64_t flags; > +} VhostUserMMap; > + > typedef struct { > VhostUserRequest request; > > @@ -224,6 +250,8 @@ typedef union { > VhostUserInflight inflight; > VhostUserShared object; > VhostUserTransferDeviceState transfer_state; > + VhostUserMMap mmap; > + VhostUserShMemConfig shmem; > } VhostUserPayload; > > typedef struct VhostUserMsg { > @@ -1771,6 +1799,196 @@ vhost_user_backend_handle_shared_object_lookup(struct > vhost_user *u, > return 0; > } > > +/** > + * vhost_user_backend_handle_shmem_map() - Handle SHMEM_MAP backend request > + * @dev: vhost device > + * @ioc: QIOChannel for communication > + * @hdr: vhost-user message header > + * @payload: message payload containing mapping details > + * @fd: file descriptor for the shared memory region > + * > + * Handles VHOST_USER_BACKEND_SHMEM_MAP requests from the backend. Creates > + * a VhostUserShmemObject to manage the shared memory mapping and adds it > + * to the appropriate VirtIO shared memory region. The VhostUserShmemObject > + * serves as an intermediate parent for the MemoryRegion, ensuring proper > + * lifecycle management with reference counting. > + * > + * Returns: 0 on success, negative errno on failure > + */ > +static int > +vhost_user_backend_handle_shmem_map(struct vhost_dev *dev, > + QIOChannel *ioc, > + VhostUserHeader *hdr, > + VhostUserPayload *payload, > + int fd) > +{ > + VirtioSharedMemory *shmem; > + VhostUserMMap *vu_mmap = &payload->mmap; > + VirtioSharedMemoryMapping *existing; > + Error *local_err = NULL; > + int ret = 0; > + > + if (fd < 0) { > + error_report("Bad fd for map"); > + ret = -EBADF; > + goto send_reply; > + } > + > + if (QSIMPLEQ_EMPTY(&dev->vdev->shmem_list)) { > + error_report("Device has no VIRTIO Shared Memory Regions. " > + "Requested ID: %d", vu_mmap->shmid); > + ret = -EFAULT; > + goto send_reply; > + } > + > + shmem = virtio_find_shmem_region(dev->vdev, vu_mmap->shmid); > + if (!shmem) { > + error_report("VIRTIO Shared Memory Region at " > + "ID %d not found or uninitialized", vu_mmap->shmid); > + ret = -EFAULT; > + goto send_reply; > + } > + > + if ((vu_mmap->shm_offset + vu_mmap->len) < vu_mmap->len || > + (vu_mmap->shm_offset + vu_mmap->len) > shmem->mr.size) { > + error_report("Bad offset/len for mmap %" PRIx64 "+%" PRIx64, > + vu_mmap->shm_offset, vu_mmap->len); > + ret = -EFAULT; > + goto send_reply; > + } > + > + QTAILQ_FOREACH(existing, &shmem->mmaps, link) { > + if (ranges_overlap(existing->offset, existing->len, > + vu_mmap->shm_offset, vu_mmap->len)) { > + error_report("VIRTIO Shared Memory mapping overlap"); > + ret = -EFAULT; > + goto send_reply; > + } > + } > + > + memory_region_transaction_begin(); > + > + /* Create VirtioSharedMemoryMapping object */ > + VirtioSharedMemoryMapping *mapping = virtio_shared_memory_mapping_new( > + vu_mmap->shmid, fd, vu_mmap->fd_offset, vu_mmap->shm_offset, > + vu_mmap->len, vu_mmap->flags & VHOST_USER_FLAG_MAP_RW); > + > + if (!mapping) { > + ret = -EFAULT; > + goto send_reply_commit; > + } > + > + /* Add the mapping to the shared memory region */ > + if (virtio_add_shmem_map(shmem, mapping) != 0) { > + error_report("Failed to add shared memory mapping"); > + object_unref(OBJECT(mapping)); > + ret = -EFAULT; > + goto send_reply_commit; > + } > + > +send_reply_commit: > + /* Send reply and commit after transaction started */ > + if (hdr->flags & VHOST_USER_NEED_REPLY_MASK) { > + payload->u64 = !!ret; > + hdr->size = sizeof(payload->u64); > + if (!vhost_user_send_resp(ioc, hdr, payload, &local_err)) { > + error_report_err(local_err); > + memory_region_transaction_commit(); > + return -EFAULT; > + } > + } > + memory_region_transaction_commit(); > + return 0; > + > +send_reply: > + if (hdr->flags & VHOST_USER_NEED_REPLY_MASK) { > + payload->u64 = !!ret; > + hdr->size = sizeof(payload->u64); > + if (!vhost_user_send_resp(ioc, hdr, payload, &local_err)) { > + error_report_err(local_err); > + return -EFAULT; > + } > + } > + return 0; > +} > + > +/** > + * vhost_user_backend_handle_shmem_unmap() - Handle SHMEM_UNMAP backend > request > + * @dev: vhost device > + * @ioc: QIOChannel for communication > + * @hdr: vhost-user message header > + * @payload: message payload containing unmapping details > + * > + * Handles VHOST_USER_BACKEND_SHMEM_UNMAP requests from the backend. Removes > + * the specified memory mapping from the VirtIO shared memory region. This > + * automatically unreferences the associated VhostUserShmemObject, which may > + * trigger its finalization and cleanup (munmap, close fd) if no other > + * references exist. > + * > + * Returns: 0 on success, negative errno on failure > + */ > +static int > +vhost_user_backend_handle_shmem_unmap(struct vhost_dev *dev, > + QIOChannel *ioc, > + VhostUserHeader *hdr, > + VhostUserPayload *payload) > +{ > + VirtioSharedMemory *shmem; > + VirtioSharedMemoryMapping *mmap = NULL; > + VhostUserMMap *vu_mmap = &payload->mmap; > + Error *local_err = NULL; > + int ret = 0; > + > + if (QSIMPLEQ_EMPTY(&dev->vdev->shmem_list)) { > + error_report("Device has no VIRTIO Shared Memory Regions. " > + "Requested ID: %d", vu_mmap->shmid); > + ret = -EFAULT; > + goto send_reply; > + } > + > + shmem = virtio_find_shmem_region(dev->vdev, vu_mmap->shmid); > + if (!shmem) { > + error_report("VIRTIO Shared Memory Region at " > + "ID %d not found or uninitialized", vu_mmap->shmid); > + ret = -EFAULT; > + goto send_reply; > + } > + > + if ((vu_mmap->shm_offset + vu_mmap->len) < vu_mmap->len || > + (vu_mmap->shm_offset + vu_mmap->len) > shmem->mr.size) { > + error_report("Bad offset/len for unmmap %" PRIx64 "+%" PRIx64, > + vu_mmap->shm_offset, vu_mmap->len); > + ret = -EFAULT; > + goto send_reply; > + } > + > + mmap = virtio_find_shmem_map(shmem, vu_mmap->shm_offset, vu_mmap->len); > + if (!mmap) { > + error_report("Shared memory mapping not found at offset %" PRIx64 > + " with length %" PRIx64, > + vu_mmap->shm_offset, vu_mmap->len); > + ret = -EFAULT; > + goto send_reply; > + } > + > +send_reply: > + if (hdr->flags & VHOST_USER_NEED_REPLY_MASK) { > + payload->u64 = !!ret; > + hdr->size = sizeof(payload->u64); > + if (!vhost_user_send_resp(ioc, hdr, payload, &local_err)) { > + error_report_err(local_err); > + return -EFAULT; > + } > + } > + > + if (!ret && mmap) { > + /* Free the MemoryRegion only after reply */ > + virtio_del_shmem_map(shmem, vu_mmap->shm_offset, vu_mmap->len); > + } > + > + return 0; > +} > + > static void close_backend_channel(struct vhost_user *u) > { > g_source_destroy(u->backend_src); > @@ -1844,6 +2062,21 @@ static gboolean backend_read(QIOChannel *ioc, > GIOCondition condition, > ret = vhost_user_backend_handle_shared_object_lookup(dev->opaque, > > &payload.object); > break; > + case VHOST_USER_BACKEND_SHMEM_MAP: > + /* Handler manages its own response, check error and close > connection */ > + reply_ack = false; > + if (vhost_user_backend_handle_shmem_map(dev, ioc, &hdr, &payload, > + fd ? fd[0] : -1) < 0) { > + goto err; > + } > + break; > + case VHOST_USER_BACKEND_SHMEM_UNMAP: > + /* Handler manages its own response, check error and close > connection */ > + reply_ack = false; > + if (vhost_user_backend_handle_shmem_unmap(dev, ioc, &hdr, &payload) > < 0) { > + goto err; > + } > + break; > default: > error_report("Received unexpected msg type: %d.", hdr.request); > ret = -EINVAL; > @@ -3021,6 +3254,41 @@ static int vhost_user_check_device_state(struct > vhost_dev *dev, Error **errp) > return 0; > } > > +static int vhost_user_get_shmem_config(struct vhost_dev *dev, > + int *nregions, > + uint64_t *memory_sizes, > + Error **errp) > +{ > + int ret; > + VhostUserMsg msg = { > + .hdr.request = VHOST_USER_GET_SHMEM_CONFIG, > + .hdr.flags = VHOST_USER_VERSION, > + }; > + > + if (!virtio_has_feature(dev->protocol_features, > + VHOST_USER_PROTOCOL_F_SHMEM)) { > + *nregions = 0; > + return 0; > + } > + > + ret = vhost_user_write(dev, &msg, NULL, 0); > + if (ret < 0) { > + return ret; > + } > + > + ret = vhost_user_read(dev, &msg); > + if (ret < 0) { > + return ret; > + } > + > + assert(msg.payload.shmem.nregions <= VIRTIO_MAX_SHMEM_REGIONS); > + *nregions = msg.payload.shmem.nregions; > + memcpy(memory_sizes, > + &msg.payload.shmem.memory_sizes, > + sizeof(uint64_t) * VIRTIO_MAX_SHMEM_REGIONS); > + return 0; > +} > + > const VhostOps user_ops = { > .backend_type = VHOST_BACKEND_TYPE_USER, > .vhost_backend_init = vhost_user_backend_init, > @@ -3059,4 +3327,5 @@ const VhostOps user_ops = { > .vhost_supports_device_state = vhost_user_supports_device_state, > .vhost_set_device_state_fd = vhost_user_set_device_state_fd, > .vhost_check_device_state = vhost_user_check_device_state, > + .vhost_get_shmem_config = vhost_user_get_shmem_config, > }; > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index 257cda506a..33186f1977 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -3090,6 +3090,173 @@ int virtio_save(VirtIODevice *vdev, QEMUFile *f) > return ret; > } > > +VirtioSharedMemory *virtio_new_shmem_region(VirtIODevice *vdev, uint8_t > shmid, uint64_t size) > +{ > + VirtioSharedMemory *elem; > + g_autofree char *name = NULL; > + > + elem = g_new0(VirtioSharedMemory, 1); > + elem->shmid = shmid; > + > + /* Initialize embedded MemoryRegion as container for shmem mappings */ > + name = g_strdup_printf("virtio-shmem-%d", shmid); > + memory_region_init(&elem->mr, OBJECT(vdev), name, size); > + QTAILQ_INIT(&elem->mmaps); > + QSIMPLEQ_INSERT_TAIL(&vdev->shmem_list, elem, entry); > + return elem; > +} > + > +VirtioSharedMemory *virtio_find_shmem_region(VirtIODevice *vdev, uint8_t > shmid) > +{ > + VirtioSharedMemory *shmem, *next; > + QSIMPLEQ_FOREACH_SAFE(shmem, &vdev->shmem_list, entry, next) { > + if (shmem->shmid == shmid) { > + return shmem; > + } > + } > + return NULL; > +} > + > +static void virtio_shared_memory_mapping_instance_init(Object *obj) > +{ > + VirtioSharedMemoryMapping *mapping = VIRTIO_SHARED_MEMORY_MAPPING(obj); > + > + mapping->shmid = 0; > + mapping->offset = 0; > + mapping->len = 0; > + mapping->mr = NULL; > +} > + > +static void virtio_shared_memory_mapping_instance_finalize(Object *obj) > +{ > + VirtioSharedMemoryMapping *mapping = VIRTIO_SHARED_MEMORY_MAPPING(obj); > + > + /* Clean up MemoryRegion if it exists */ > + if (mapping->mr) { > + /* Unparent the MemoryRegion to trigger cleanup */ > + object_unparent(OBJECT(mapping->mr)); > + mapping->mr = NULL; > + } > +} > + > +VirtioSharedMemoryMapping *virtio_shared_memory_mapping_new(uint8_t shmid, > + int fd, > + uint64_t > fd_offset, > + uint64_t > shm_offset, > + uint64_t len, > + bool allow_write) > +{ > + VirtioSharedMemoryMapping *mapping; > + MemoryRegion *mr; > + g_autoptr(GString) mr_name = g_string_new(NULL); > + uint32_t ram_flags; > + Error *local_err = NULL; > + > + if (len == 0) { > + error_report("Shared memory mapping size cannot be zero"); > + return NULL; > + } > + > + fd = dup(fd); > + if (fd < 0) { > + error_report("Failed to duplicate fd: %s", strerror(errno)); > + return NULL; > + } > + > + /* Determine RAM flags */ > + ram_flags = RAM_SHARED; > + if (!allow_write) { > + ram_flags |= RAM_READONLY_FD; > + } > + > + /* Create the VirtioSharedMemoryMapping */ > + mapping = VIRTIO_SHARED_MEMORY_MAPPING( > + object_new(TYPE_VIRTIO_SHARED_MEMORY_MAPPING)); > + > + /* Set up object properties */ > + mapping->shmid = shmid; > + mapping->offset = shm_offset; > + mapping->len = len; > + > + /* Create MemoryRegion as a child of this object */ > + mr = g_new0(MemoryRegion, 1); > + g_string_printf(mr_name, "virtio-shmem-%d-%" PRIx64, shmid, shm_offset); > + > + /* Initialize MemoryRegion with file descriptor */ > + if (!memory_region_init_ram_from_fd(mr, OBJECT(mapping), mr_name->str, > + len, ram_flags, fd, fd_offset, > + &local_err)) { > + error_report_err(local_err); > + g_free(mr); > + close(fd); > + object_unref(OBJECT(mapping)); > + return NULL; > + } > + > + mapping->mr = mr; > + return mapping; > +} > + > +int virtio_add_shmem_map(VirtioSharedMemory *shmem, > + VirtioSharedMemoryMapping *mapping) > +{ > + if (!mapping) { > + error_report("VirtioSharedMemoryMapping cannot be NULL"); > + return -1; > + } > + if (!mapping->mr) { > + error_report("VirtioSharedMemoryMapping has no MemoryRegion"); > + return -1; > + } > + > + /* Validate boundaries against the VIRTIO shared memory region */ > + if (mapping->offset + mapping->len > shmem->mr.size) { > + error_report("Memory exceeds the shared memory boundaries"); > + return -1; > + } > + > + /* Add as subregion to the VIRTIO shared memory */ > + memory_region_add_subregion(&shmem->mr, mapping->offset, mapping->mr); > + > + /* Add to the mapped regions list */ > + QTAILQ_INSERT_TAIL(&shmem->mmaps, mapping, link); > + > + return 0; > +} > + > +VirtioSharedMemoryMapping *virtio_find_shmem_map(VirtioSharedMemory *shmem, > + hwaddr offset, uint64_t size) > +{ > + VirtioSharedMemoryMapping *mapping; > + QTAILQ_FOREACH(mapping, &shmem->mmaps, link) { > + if (mapping->offset == offset && mapping->mr->size == size) { > + return mapping; > + } > + } > + return NULL; > +} > + > +void virtio_del_shmem_map(VirtioSharedMemory *shmem, hwaddr offset, > + uint64_t size) > +{ > + VirtioSharedMemoryMapping *mapping = virtio_find_shmem_map(shmem, > offset, size); > + if (mapping == NULL) { > + return; > + } > + > + /* > + * Remove from memory region first > + */ > + memory_region_del_subregion(&shmem->mr, mapping->mr); > + > + /* > + * Remove from list and unref the mapping which will trigger automatic > cleanup > + * when the reference count reaches zero. > + */ > + QTAILQ_REMOVE(&shmem->mmaps, mapping, link); > + object_unref(OBJECT(mapping)); > +} > + > /* A wrapper for use as a VMState .put function */ > static int virtio_device_put(QEMUFile *f, void *opaque, size_t size, > const VMStateField *field, JSONWriter *vmdesc) > @@ -3216,6 +3383,7 @@ void virtio_reset(void *opaque) > { > VirtIODevice *vdev = opaque; > VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev); > + VirtioSharedMemory *shmem; > uint64_t features[VIRTIO_FEATURES_NU64S]; > int i; > > @@ -3255,6 +3423,14 @@ void virtio_reset(void *opaque) > for (i = 0; i < VIRTIO_QUEUE_MAX; i++) { > __virtio_queue_reset(vdev, i); > } > + > + /* Mappings are removed to prevent stale fds from remaining open. */ > + QSIMPLEQ_FOREACH(shmem, &vdev->shmem_list, entry) { > + while (!QTAILQ_EMPTY(&shmem->mmaps)) { > + VirtioSharedMemoryMapping *mapping = QTAILQ_FIRST(&shmem->mmaps); > + virtio_del_shmem_map(shmem, mapping->offset, mapping->mr->size); > + } > + } > } > > static void virtio_device_check_notification_compatibility(VirtIODevice > *vdev, > @@ -3578,6 +3754,7 @@ void virtio_init(VirtIODevice *vdev, uint16_t > device_id, size_t config_size) > NULL, virtio_vmstate_change, vdev); > vdev->device_endian = virtio_default_endian(); > vdev->use_guest_notifier_mask = true; > + QSIMPLEQ_INIT(&vdev->shmem_list); > } > > /* > @@ -4089,11 +4266,24 @@ static void > virtio_device_free_virtqueues(VirtIODevice *vdev) > static void virtio_device_instance_finalize(Object *obj) > { > VirtIODevice *vdev = VIRTIO_DEVICE(obj); > + VirtioSharedMemory *shmem; > > virtio_device_free_virtqueues(vdev); > > g_free(vdev->config); > g_free(vdev->vector_queues); > + while (!QSIMPLEQ_EMPTY(&vdev->shmem_list)) { > + shmem = QSIMPLEQ_FIRST(&vdev->shmem_list); > + while (!QTAILQ_EMPTY(&shmem->mmaps)) { > + VirtioSharedMemoryMapping *mapping = QTAILQ_FIRST(&shmem->mmaps); > + virtio_del_shmem_map(shmem, mapping->offset, mapping->mr->size); > + } > + > + /* Clean up the embedded MemoryRegion */ > + object_unparent(OBJECT(&shmem->mr)); > + QSIMPLEQ_REMOVE_HEAD(&vdev->shmem_list, entry); > + g_free(shmem); > + } > } > > static const Property virtio_properties[] = { > @@ -4459,9 +4649,18 @@ static const TypeInfo virtio_device_info = { > .class_size = sizeof(VirtioDeviceClass), > }; > > +static const TypeInfo virtio_shared_memory_mapping_info = { > + .name = TYPE_VIRTIO_SHARED_MEMORY_MAPPING, > + .parent = TYPE_OBJECT, > + .instance_size = sizeof(VirtioSharedMemoryMapping), > + .instance_init = virtio_shared_memory_mapping_instance_init, > + .instance_finalize = virtio_shared_memory_mapping_instance_finalize, > +}; > + > static void virtio_register_types(void) > { > type_register_static(&virtio_device_info); > + type_register_static(&virtio_shared_memory_mapping_info); > } > > type_init(virtio_register_types) > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h > index d97529c3f1..3f6dfba321 100644 > --- a/include/hw/virtio/virtio.h > +++ b/include/hw/virtio/virtio.h > @@ -99,6 +99,45 @@ enum virtio_device_endian { > VIRTIO_DEVICE_ENDIAN_BIG, > }; > > +#define TYPE_VIRTIO_SHARED_MEMORY_MAPPING "virtio-shared-memory-mapping" > +OBJECT_DECLARE_SIMPLE_TYPE(VirtioSharedMemoryMapping, > VIRTIO_SHARED_MEMORY_MAPPING) > + > +/** > + * VirtioSharedMemoryMapping: > + * @parent: Parent QOM object > + * @shmid: VIRTIO Shared Memory Region ID > + * @fd: File descriptor for the shared memory region > + * @offset: Offset within the VIRTIO Shared Memory Region > + * @len: Size of the mapping > + * @mr: MemoryRegion associated with this shared memory mapping > + * @link: List entry for the shared memory region's mapping list > + * > + * A QOM object that represents an individual file descriptor-based shared > + * memory mapping within a VIRTIO Shared Memory Region. It manages the > + * MemoryRegion lifecycle and file descriptor cleanup through QOM reference > + * counting. When the object is unreferenced and its reference count drops > + * to zero, it automatically cleans up the MemoryRegion and closes the file > + * descriptor. > + */ > +struct VirtioSharedMemoryMapping { > + Object parent; > + > + uint8_t shmid; > + hwaddr offset; > + uint64_t len; > + MemoryRegion *mr; > + QTAILQ_ENTRY(VirtioSharedMemoryMapping) link; > +}; > + > +struct VirtioSharedMemory { > + uint8_t shmid; > + MemoryRegion mr; > + QTAILQ_HEAD(, VirtioSharedMemoryMapping) mmaps; > + QSIMPLEQ_ENTRY(VirtioSharedMemory) entry; > +}; > + > +typedef struct VirtioSharedMemory VirtioSharedMemory; > + > /** > * struct VirtIODevice - common VirtIO structure > * @name: name of the device > @@ -168,6 +207,8 @@ struct VirtIODevice > */ > EventNotifier config_notifier; > bool device_iotlb_enabled; > + /* Shared memory region for mappings. */ > + QSIMPLEQ_HEAD(, VirtioSharedMemory) shmem_list; > }; > > struct VirtioDeviceClass { > @@ -298,6 +339,100 @@ void virtio_notify(VirtIODevice *vdev, VirtQueue *vq); > > int virtio_save(VirtIODevice *vdev, QEMUFile *f); > > +/** > + * virtio_new_shmem_region() - Create a new shared memory region > + * @vdev: VirtIODevice > + * @shmid: Shared memory ID > + * @size: Size of the shared memory region > + * > + * Creates a new VirtioSharedMemory region for the given device and ID. > + * The returned VirtioSharedMemory is owned by the VirtIODevice and will > + * be automatically freed when the device is destroyed. The caller > + * should not free the returned pointer. > + * > + * Returns: Pointer to the new VirtioSharedMemory region, or NULL on failure > + */ > +VirtioSharedMemory *virtio_new_shmem_region(VirtIODevice *vdev, uint8_t > shmid, uint64_t size); > + > +/** > + * virtio_find_shmem_region() - Find an existing shared memory region > + * @vdev: VirtIODevice > + * @shmid: Shared memory ID to find > + * > + * Finds an existing VirtioSharedMemory region by ID. The returned pointer > + * is owned by the VirtIODevice and should not be freed by the caller. > + * > + * Returns: Pointer to the VirtioSharedMemory region, or NULL if not found > + */ > +VirtioSharedMemory *virtio_find_shmem_region(VirtIODevice *vdev, uint8_t > shmid); > + > +/** > + * virtio_shared_memory_mapping_new() - Create a new > VirtioSharedMemoryMapping > + * @shmid: VIRTIO Shared Memory Region ID > + * @fd: File descriptor for the shared memory > + * @fd_offset: Offset within the file descriptor > + * @shm_offset: Offset within the VIRTIO Shared Memory Region > + * @len: Size of the mapping > + * @allow_write: Whether to allow write access to the mapping > + * > + * Creates a new VirtioSharedMemoryMapping that manages a shared memory > mapping. > + * The object will create a MemoryRegion using > memory_region_init_ram_from_fd() > + * as a child object. When the object is finalized, it will automatically > + * clean up the MemoryRegion and close the file descriptor. > + * > + * Return: A new VirtioSharedMemoryMapping on success, NULL on error. > + */ > +VirtioSharedMemoryMapping *virtio_shared_memory_mapping_new(uint8_t shmid, > + int fd, > + uint64_t > fd_offset, > + uint64_t > shm_offset, > + uint64_t len, > + bool > allow_write); > + > +/** > + * virtio_add_shmem_map() - Add a memory mapping to a shared region > + * @shmem: VirtioSharedMemory region > + * @mapping: VirtioSharedMemoryMapping to add (transfers ownership) > + * > + * Adds a memory mapping to the shared memory region. The > VirtioSharedMemoryMapping > + * ownership is transferred to the shared memory region and will be > automatically > + * cleaned up through QOM reference counting when virtio_del_shmem_map() is > + * called or when the shared memory region is destroyed. > + * > + * Returns: 0 on success, negative errno on failure > + */ > +int virtio_add_shmem_map(VirtioSharedMemory *shmem, > + VirtioSharedMemoryMapping *mapping); > + > +/** > + * virtio_find_shmem_map() - Find a memory mapping in a shared region > + * @shmem: VirtioSharedMemory region > + * @offset: Offset within the shared memory region > + * @size: Size of the mapping to find > + * > + * Finds an existing memory mapping that covers the specified range. > + * The returned VirtioSharedMemoryMapping is owned by the VirtioSharedMemory > + * region and should not be freed by the caller. > + * > + * Returns: Pointer to the VirtioSharedMemoryMapping, or NULL if not found > + */ > +VirtioSharedMemoryMapping *virtio_find_shmem_map(VirtioSharedMemory *shmem, > + hwaddr offset, uint64_t size); > + > +/** > + * virtio_del_shmem_map() - Remove a memory mapping from a shared region > + * @shmem: VirtioSharedMemory region > + * @offset: Offset of the mapping to remove > + * @size: Size of the mapping to remove > + * > + * Removes a memory mapping from the shared memory region. This will > + * automatically unref the associated VhostUserShmemObject, which may > + * trigger its finalization and cleanup if no other references exist. > + * The mapping's MemoryRegion will be properly unmapped and cleaned up. > + */ > +void virtio_del_shmem_map(VirtioSharedMemory *shmem, hwaddr offset, > + uint64_t size); > + > extern const VMStateInfo virtio_vmstate_info; > > #define VMSTATE_VIRTIO_DEVICE \ > diff --git a/subprojects/libvhost-user/libvhost-user.c > b/subprojects/libvhost-user/libvhost-user.c > index 9c630c2170..034cbfdc3c 100644 > --- a/subprojects/libvhost-user/libvhost-user.c > +++ b/subprojects/libvhost-user/libvhost-user.c > @@ -1592,6 +1592,76 @@ vu_rm_shared_object(VuDev *dev, unsigned char > uuid[UUID_LEN]) > return vu_send_message(dev, &msg); > } > > +bool > +vu_shmem_map(VuDev *dev, uint8_t shmid, uint64_t fd_offset, > + uint64_t shm_offset, uint64_t len, uint64_t flags, int fd) > +{ > + VhostUserMsg vmsg = { > + .request = VHOST_USER_BACKEND_SHMEM_MAP, > + .size = sizeof(vmsg.payload.mmap), > + .flags = VHOST_USER_VERSION, > + .payload.mmap = { > + .shmid = shmid, > + .fd_offset = fd_offset, > + .shm_offset = shm_offset, > + .len = len, > + .flags = flags, > + }, > + .fd_num = 1, > + .fds[0] = fd, > + }; > + > + if (!vu_has_protocol_feature(dev, VHOST_USER_PROTOCOL_F_SHMEM)) { > + return false; > + } > + > + if (vu_has_protocol_feature(dev, VHOST_USER_PROTOCOL_F_REPLY_ACK)) { > + vmsg.flags |= VHOST_USER_NEED_REPLY_MASK; > + } > + > + pthread_mutex_lock(&dev->backend_mutex); > + if (!vu_message_write(dev, dev->backend_fd, &vmsg)) { > + pthread_mutex_unlock(&dev->backend_mutex); > + return false; > + } > + > + /* Also unlocks the backend_mutex */ > + return vu_process_message_reply(dev, &vmsg); > +} > + > +bool > +vu_shmem_unmap(VuDev *dev, uint8_t shmid, uint64_t shm_offset, uint64_t len) > +{ > + VhostUserMsg vmsg = { > + .request = VHOST_USER_BACKEND_SHMEM_UNMAP, > + .size = sizeof(vmsg.payload.mmap), > + .flags = VHOST_USER_VERSION, > + .payload.mmap = { > + .shmid = shmid, > + .fd_offset = 0, > + .shm_offset = shm_offset, > + .len = len, > + }, > + }; > + > + if (!vu_has_protocol_feature(dev, VHOST_USER_PROTOCOL_F_SHMEM)) { > + return false; > + } > + > + if (vu_has_protocol_feature(dev, VHOST_USER_PROTOCOL_F_REPLY_ACK)) { > + vmsg.flags |= VHOST_USER_NEED_REPLY_MASK; > + } > + > + pthread_mutex_lock(&dev->backend_mutex); > + if (!vu_message_write(dev, dev->backend_fd, &vmsg)) { > + pthread_mutex_unlock(&dev->backend_mutex); > + return false; > + } > + > + /* Also unlocks the backend_mutex */ > + return vu_process_message_reply(dev, &vmsg); > +} > + > static bool > vu_set_vring_call_exec(VuDev *dev, VhostUserMsg *vmsg) > { > diff --git a/subprojects/libvhost-user/libvhost-user.h > b/subprojects/libvhost-user/libvhost-user.h > index 2ffc58c11b..6a2d0f9fae 100644 > --- a/subprojects/libvhost-user/libvhost-user.h > +++ b/subprojects/libvhost-user/libvhost-user.h > @@ -69,6 +69,8 @@ enum VhostUserProtocolFeature { > /* Feature 16 is reserved for VHOST_USER_PROTOCOL_F_STATUS. */ > /* Feature 17 reserved for VHOST_USER_PROTOCOL_F_XEN_MMAP. */ > VHOST_USER_PROTOCOL_F_SHARED_OBJECT = 18, > + /* Feature 19 is reserved for VHOST_USER_PROTOCOL_F_DEVICE_STATE */ > + VHOST_USER_PROTOCOL_F_SHMEM = 20, > VHOST_USER_PROTOCOL_F_MAX > }; > > @@ -127,6 +129,8 @@ typedef enum VhostUserBackendRequest { > VHOST_USER_BACKEND_SHARED_OBJECT_ADD = 6, > VHOST_USER_BACKEND_SHARED_OBJECT_REMOVE = 7, > VHOST_USER_BACKEND_SHARED_OBJECT_LOOKUP = 8, > + VHOST_USER_BACKEND_SHMEM_MAP = 9, > + VHOST_USER_BACKEND_SHMEM_UNMAP = 10, > VHOST_USER_BACKEND_MAX > } VhostUserBackendRequest; > > @@ -186,6 +190,23 @@ typedef struct VhostUserShared { > unsigned char uuid[UUID_LEN]; > } VhostUserShared; > > +/* For the flags field of VhostUserMMap */ > +#define VHOST_USER_FLAG_MAP_RW (1u << 0) > + > +typedef struct { > + /* VIRTIO Shared Memory Region ID */ > + uint8_t shmid; > + uint8_t padding[7]; > + /* File offset */ > + uint64_t fd_offset; > + /* Offset within the VIRTIO Shared Memory Region */ > + uint64_t shm_offset; > + /* Size of the mapping */ > + uint64_t len; > + /* Flags for the mmap operation, from VHOST_USER_FLAG_MAP_* */ > + uint64_t flags; > +} VhostUserMMap; > + > #define VU_PACKED __attribute__((packed)) > > typedef struct VhostUserMsg { > @@ -210,6 +231,7 @@ typedef struct VhostUserMsg { > VhostUserVringArea area; > VhostUserInflight inflight; > VhostUserShared object; > + VhostUserMMap mmap; > } payload; > > int fds[VHOST_MEMORY_BASELINE_NREGIONS]; > @@ -593,6 +615,38 @@ bool vu_add_shared_object(VuDev *dev, unsigned char > uuid[UUID_LEN]); > */ > bool vu_rm_shared_object(VuDev *dev, unsigned char uuid[UUID_LEN]); > > +/** > + * vu_shmem_map: > + * @dev: a VuDev context > + * @shmid: VIRTIO Shared Memory Region ID > + * @fd_offset: File offset > + * @shm_offset: Offset within the VIRTIO Shared Memory Region > + * @len: Size of the mapping > + * @flags: Flags for the mmap operation > + * @fd: A file descriptor > + * > + * Advertises a new mapping to be made in a given VIRTIO Shared Memory > Region. > + * > + * Returns: TRUE on success, FALSE on failure. > + */ > +bool vu_shmem_map(VuDev *dev, uint8_t shmid, uint64_t fd_offset, > + uint64_t shm_offset, uint64_t len, uint64_t flags, int fd); > + > +/** > + * vu_shmem_unmap: > + * @dev: a VuDev context > + * @shmid: VIRTIO Shared Memory Region ID > + * @fd_offset: File offset > + * @len: Size of the mapping > + * > + * The front-end un-mmaps a given range in the VIRTIO Shared Memory Region > + * with the requested `shmid`. > + * > + * Returns: TRUE on success, FALSE on failure. > + */ > +bool vu_shmem_unmap(VuDev *dev, uint8_t shmid, uint64_t shm_offset, > + uint64_t len); > + > /** > * vu_queue_set_notification: > * @dev: a VuDev context > -- > 2.49.0
