Add SHMEM_MAP/UNMAP requests to vhost-user to handle VIRTIO Shared Memory mappings.
This request allows backends to dynamically map fds into a VIRTIO Shared Memory Region indentified by its `shmid`. Then, the fd memory is advertised to the driver as a base addres + offset, so it can be read/written (depending on the mmap flags requested) while its valid. The backend can munmap the memory range in a given VIRTIO Shared Memory Region (again, identified by its `shmid`), to free it. Upon receiving this message, the front-end must mmap the regions with PROT_NONE to reserve the virtual memory space. The device model needs to create MemoryRegion instances for the VIRTIO Shared Memory Regions and add them to the `VirtIODevice` instance. Signed-off-by: Albert Esteve <aest...@redhat.com> --- docs/interop/vhost-user.rst | 27 +++++ hw/virtio/vhost-user.c | 122 ++++++++++++++++++++++ hw/virtio/virtio.c | 12 +++ include/hw/virtio/virtio.h | 5 + subprojects/libvhost-user/libvhost-user.c | 65 ++++++++++++ subprojects/libvhost-user/libvhost-user.h | 53 ++++++++++ 6 files changed, 284 insertions(+) diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst index d8419fd2f1..d52ba719d5 100644 --- a/docs/interop/vhost-user.rst +++ b/docs/interop/vhost-user.rst @@ -1859,6 +1859,33 @@ is sent by the front-end. when the operation is successful, or non-zero otherwise. Note that if the operation fails, no fd is sent to the backend. +``VHOST_USER_BACKEND_SHMEM_MAP`` + :id: 9 + :equivalent ioctl: N/A + :request payload: fd and ``struct VhostUserMMap`` + :reply payload: N/A + + This message can be submitted by the backends to advertise a new mapping + to be made in a given VIRTIO Shared Memory Region. Upon receiving the message, + The front-end will mmap the given fd into the VIRTIO Shared Memory Region + with the requested ``shmid``. A reply is generated indicating whether mapping + succeeded. + + Mapping over an already existing map is not allowed and request shall fail. + Therefore, the memory range in the request must correspond with a valid, + free region of the VIRTIO Shared Memory Region. + +``VHOST_USER_BACKEND_SHMEM_UNMAP`` + :id: 10 + :equivalent ioctl: N/A + :request payload: ``struct VhostUserMMap`` + :reply payload: N/A + + This message can be submitted by the backends so that the front-end un-mmap + a given range (``offset``, ``len``) in the VIRTIO Shared Memory Region with + the requested ``shmid``. + A reply is generated indicating whether unmapping succeeded. + .. _reply_ack: VHOST_USER_PROTOCOL_F_REPLY_ACK diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index cdf9af4a4b..7ee8a472c6 100644 --- a/hw/virtio/vhost-user.c +++ b/hw/virtio/vhost-user.c @@ -115,6 +115,8 @@ 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; @@ -192,6 +194,24 @@ typedef struct VhostUserShared { unsigned char uuid[16]; } VhostUserShared; +/* For the flags field of VhostUserMMap */ +#define VHOST_USER_FLAG_MAP_R (1u << 0) +#define VHOST_USER_FLAG_MAP_W (1u << 1) + +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_* */ + uint64_t flags; +} VhostUserMMap; + typedef struct { VhostUserRequest request; @@ -224,6 +244,7 @@ typedef union { VhostUserInflight inflight; VhostUserShared object; VhostUserTransferDeviceState transfer_state; + VhostUserMMap mmap; } VhostUserPayload; typedef struct VhostUserMsg { @@ -1748,6 +1769,100 @@ vhost_user_backend_handle_shared_object_lookup(struct vhost_user *u, return 0; } +static int +vhost_user_backend_handle_shmem_map(struct vhost_dev *dev, + VhostUserMMap *vu_mmap, + int fd) +{ + void *addr = 0; + MemoryRegion *mr = NULL; + + if (fd < 0) { + error_report("Bad fd for map"); + return -EBADF; + } + + if (!dev->vdev->shmem_list || + dev->vdev->n_shmem_regions <= vu_mmap->shmid) { + error_report("Device only has %d VIRTIO Shared Memory Regions. " + "Requested ID: %d", + dev->vdev->n_shmem_regions, vu_mmap->shmid); + return -EFAULT; + } + + mr = &dev->vdev->shmem_list[vu_mmap->shmid]; + + if (!mr) { + error_report("VIRTIO Shared Memory Region at " + "ID %d unitialized", vu_mmap->shmid); + return -EFAULT; + } + + if ((vu_mmap->shm_offset + vu_mmap->len) < vu_mmap->len || + (vu_mmap->shm_offset + vu_mmap->len) > mr->size) { + error_report("Bad offset/len for mmap %" PRIx64 "+%" PRIx64, + vu_mmap->shm_offset, vu_mmap->len); + return -EFAULT; + } + + void *shmem_ptr = memory_region_get_ram_ptr(mr); + + addr = mmap(shmem_ptr + vu_mmap->shm_offset, vu_mmap->len, + ((vu_mmap->flags & VHOST_USER_FLAG_MAP_R) ? PROT_READ : 0) | + ((vu_mmap->flags & VHOST_USER_FLAG_MAP_W) ? PROT_WRITE : 0), + MAP_SHARED | MAP_FIXED, fd, vu_mmap->fd_offset); + + if (addr == MAP_FAILED) { + error_report("Failed to mmap mem fd"); + return -EFAULT; + } + + return 0; +} + +static int +vhost_user_backend_handle_shmem_unmap(struct vhost_dev *dev, + VhostUserMMap *vu_mmap) +{ + void *addr = 0; + MemoryRegion *mr = NULL; + + if (!dev->vdev->shmem_list || + dev->vdev->n_shmem_regions <= vu_mmap->shmid) { + error_report("Device only has %d VIRTIO Shared Memory Regions. " + "Requested ID: %d", + dev->vdev->n_shmem_regions, vu_mmap->shmid); + return -EFAULT; + } + + mr = &dev->vdev->shmem_list[vu_mmap->shmid]; + + if (!mr) { + error_report("VIRTIO Shared Memory Region at " + "ID %d unitialized", vu_mmap->shmid); + return -EFAULT; + } + + if ((vu_mmap->shm_offset + vu_mmap->len) < vu_mmap->len || + (vu_mmap->shm_offset + vu_mmap->len) > mr->size) { + error_report("Bad offset/len for mmap %" PRIx64 "+%" PRIx64, + vu_mmap->shm_offset, vu_mmap->len); + return -EFAULT; + } + + void *shmem_ptr = memory_region_get_ram_ptr(mr); + + addr = mmap(shmem_ptr + vu_mmap->shm_offset, vu_mmap->len, + PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0); + + if (addr == MAP_FAILED) { + error_report("Failed to unmap memory"); + return -EFAULT; + } + + return 0; +} + static void close_backend_channel(struct vhost_user *u) { g_source_destroy(u->backend_src); @@ -1816,6 +1931,13 @@ static gboolean backend_read(QIOChannel *ioc, GIOCondition condition, ret = vhost_user_backend_handle_shared_object_lookup(dev->opaque, ioc, &hdr, &payload); break; + case VHOST_USER_BACKEND_SHMEM_MAP: + ret = vhost_user_backend_handle_shmem_map(dev, &payload.mmap, + fd ? fd[0] : -1); + break; + case VHOST_USER_BACKEND_SHMEM_UNMAP: + ret = vhost_user_backend_handle_shmem_unmap(dev, &payload.mmap); + break; default: error_report("Received unexpected msg type: %d.", hdr.request); ret = -EINVAL; diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 893a072c9d..9f2da5b11e 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -2856,6 +2856,16 @@ int virtio_save(VirtIODevice *vdev, QEMUFile *f) return vmstate_save_state(f, &vmstate_virtio, vdev, NULL); } +MemoryRegion *virtio_new_shmem_region(VirtIODevice *vdev) +{ + MemoryRegion *mr = g_new0(MemoryRegion, 1); + ++vdev->n_shmem_regions; + vdev->shmem_list = g_renew(MemoryRegion, vdev->shmem_list, + vdev->n_shmem_regions); + vdev->shmem_list[vdev->n_shmem_regions - 1] = *mr; + return mr; +} + /* 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) @@ -3264,6 +3274,8 @@ void virtio_init(VirtIODevice *vdev, uint16_t device_id, size_t config_size) virtio_vmstate_change, vdev); vdev->device_endian = virtio_default_endian(); vdev->use_guest_notifier_mask = true; + vdev->shmem_list = NULL; + vdev->n_shmem_regions = 0; } /* diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h index 7d5ffdc145..16d598aadc 100644 --- a/include/hw/virtio/virtio.h +++ b/include/hw/virtio/virtio.h @@ -165,6 +165,9 @@ struct VirtIODevice */ EventNotifier config_notifier; bool device_iotlb_enabled; + /* Shared memory region for vhost-user mappings. */ + MemoryRegion *shmem_list; + int n_shmem_regions; }; struct VirtioDeviceClass { @@ -280,6 +283,8 @@ void virtio_notify(VirtIODevice *vdev, VirtQueue *vq); int virtio_save(VirtIODevice *vdev, QEMUFile *f); +MemoryRegion *virtio_new_shmem_region(VirtIODevice *vdev); + 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 a879149fef..28556d183a 100644 --- a/subprojects/libvhost-user/libvhost-user.c +++ b/subprojects/libvhost-user/libvhost-user.c @@ -1586,6 +1586,71 @@ 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) +{ + bool result = false; + VhostUserMsg msg_reply; + 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, + }, + }; + + 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 fd_offset, + uint64_t shm_offset, uint64_t len) +{ + bool result = false; + VhostUserMsg msg_reply; + VhostUserMsg vmsg = { + .request = VHOST_USER_BACKEND_SHMEM_UNMAP, + .size = sizeof(vmsg.payload.mmap), + .flags = VHOST_USER_VERSION, + .payload.mmap = { + .shmid = shmid, + .fd_offset = fd_offset, + .shm_offset = shm_offset, + .len = len, + }, + }; + + 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 deb40e77b3..7f6c22cc1a 100644 --- a/subprojects/libvhost-user/libvhost-user.h +++ b/subprojects/libvhost-user/libvhost-user.h @@ -127,6 +127,8 @@ 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 +188,24 @@ typedef struct VhostUserShared { unsigned char uuid[UUID_LEN]; } VhostUserShared; +/* For the flags field of VhostUserMMap */ +#define VHOST_USER_FLAG_MAP_R (1u << 0) +#define VHOST_USER_FLAG_MAP_W (1u << 1) + +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_* */ + uint64_t flags; +} VhostUserMMap; + #if defined(_WIN32) && (defined(__x86_64__) || defined(__i386__)) # define VU_PACKED __attribute__((gcc_struct, packed)) #else @@ -214,6 +234,7 @@ typedef struct VhostUserMsg { VhostUserVringArea area; VhostUserInflight inflight; VhostUserShared object; + VhostUserMMap mmap; } payload; int fds[VHOST_MEMORY_BASELINE_NREGIONS]; @@ -597,6 +618,38 @@ 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 + * + * 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); + +/** + * 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 + * + * 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 fd_offset, + uint64_t shm_offset, uint64_t len); + /** * vu_queue_set_notification: * @dev: a VuDev context -- 2.45.2