On Thu, Oct 16, 2025 at 4:43 PM Albert Esteve <[email protected]> wrote:
>
> On Wed, Oct 15, 2025 at 2:51 PM Manos Pitsidianakis
> <[email protected]> wrote:
> >
> > On Wed, 15 Oct 2025 15:29, Albert Esteve <[email protected]> wrote:
> > >On Wed, Oct 15, 2025 at 11:52 AM Manos Pitsidianakis
> > ><[email protected]> wrote:
> > >>
> > >> On Wed, 15 Oct 2025 11:59, Albert Esteve <[email protected]> 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.
> > >> >
> > >> >Signed-off-by: Albert Esteve <[email protected]>
> > >> >---
> > >> > hw/virtio/vhost-user.c | 213 ++++++++++++++++++++++
> > >> > hw/virtio/virtio.c | 207 +++++++++++++++++++++
> > >> > include/hw/virtio/virtio.h | 136 ++++++++++++++
> > >> > subprojects/libvhost-user/libvhost-user.c | 70 +++++++
> > >> > subprojects/libvhost-user/libvhost-user.h | 54 ++++++
> > >> > 5 files changed, 680 insertions(+)
> > >> >
> > >> >diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > >> >index 36c9c2e04d..8a4385a5ad 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 +194,23 @@ 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 +243,7 @@ typedef union {
> > >> > VhostUserInflight inflight;
> > >> > VhostUserShared object;
> > >> > VhostUserTransferDeviceState transfer_state;
> > >> >+ VhostUserMMap mmap;
> > >> > } VhostUserPayload;
> > >> >
> > >> > typedef struct VhostUserMsg {
> > >> >@@ -1768,6 +1788,186 @@
> > >> >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;
> > >>
> > >> Apologies if I missed something obvious, but won't going to send_reply
> > >> at this point cause memory_region_transaction_commit() to be called?
> > >> Maybe we should have two cleanup labels, depending on whether
> > >> memory_region_transaction_begin() has been called yet?
> > >
> > >You are right, this is not good, at transaction_depth 0 it would fail
> > >an assertion within memory_region_transaction_commit().
> > >
> > >Not sure another cleanup label will work, though, as the transaction
> > >commit has to go after the reply. Maybe we can make the reply within
> > >the handler optional (leveraging the REPLY_MASK flag). But that will
> > >need to be tuned when this patch lands:
> > >https://lists.gnu.org/archive/html/qemu-devel/2025-10/msg03632.html
> > >
> > >Or just a simpler solution like this would do?
> >
> >
> > Yes this looks like enough. The another cleanup label alternative I
> > meant would be to do:
> >
> > +send_reply_no_commit:
> > + 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;
> > +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);
> > + memory_region_transaction_commit();
> > + return -EFAULT;
> > + }
> > + }
> > +
> > + memory_region_transaction_commit();
> > +
> > + return 0;
> > +}
> >
> > But this is not much prettier. (In rust this would be trivial with a MR
> > transaction RAII object...)
>
> I tried this solution too and it fails with `Illegal instruction (core
> dumped)`. I am not sure why, the logic should be basically the same.
> It has me puzzled.
>
> So... I'll use the boolean variable solution. That one seems to work fine.
Sounds like you're hitting the abort, because `send_reply_no_commit`
is first, and it runs on success (it should be after `send_reply`).
Oops :)
>
> >
> > >
> > >diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > >index c39cf52dbc..46126eed3b 100644
> > >--- a/hw/virtio/vhost-user.c
> > >+++ b/hw/virtio/vhost-user.c
> > >@@ -1824,6 +1824,7 @@ vhost_user_backend_handle_shmem_map(struct vhost_dev
> > >*dev,
> > > VirtioSharedMemoryMapping *existing;
> > > Error *local_err = NULL;
> > > int ret = 0;
> > >+ bool transaction_started = false;
> > >
> > > if (fd < 0) {
> > > error_report("Bad fd for map");
> > >@@ -1864,6 +1865,7 @@ vhost_user_backend_handle_shmem_map(struct vhost_dev
> > >*dev,
> > > }
> > >
> > > memory_region_transaction_begin();
> > >+ transaction_started = true;
> > >
> > > /* Create VirtioSharedMemoryMapping object */
> > > VirtioSharedMemoryMapping *mapping = virtio_shared_memory_mapping_new(
> > >@@ -1889,14 +1891,18 @@ send_reply:
> > > hdr->size = sizeof(payload->u64);
> > > if (!vhost_user_send_resp(ioc, hdr, payload, &local_err)) {
> > > error_report_err(local_err);
> > >- memory_region_transaction_commit();
> > >+ if (transaction_started) {
> > >+ memory_region_transaction_commit();
> > >+ }
> > > return -EFAULT;
> > > }
> > > }
> > >
> > >- memory_region_transaction_commit();
> > >-
> > >- return 0;
> > >+ /* Only commit if we started a transaction */
> > >+ if (transaction_started) {
> > >+ memory_region_transaction_commit();
> > >+ }
> > >+ return ret;
> > > }
> > >
> > >>
> > >> >+ }
> > >> >+
> > >> >+ 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;
> > >> >+ }
> > >> >+
> > >> >+ /* 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;
> > >> >+ }
> > >> >+
> > >> >+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);
> > >> >+ memory_region_transaction_commit();
> > >> >+ return -EFAULT;
> > >> >+ }
> > >> >+ }
> > >> >+
> > >> >+ memory_region_transaction_commit();
> > >> >+
> > >> >+ 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);
> > >> >@@ -1836,6 +2036,19 @@ 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:
> > >> >+ /* Handler manages its own response, check error and close
> > >> >connection */
> > >> >+ 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 */
> > >> >+ 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;
> > >> >diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> > >> >index 153ee0a0cf..37070e7951 100644
> > >> >--- a/hw/virtio/virtio.c
> > >> >+++ b/hw/virtio/virtio.c
> > >> >@@ -3086,6 +3086,181 @@ int virtio_save(VirtIODevice *vdev, QEMUFile *f)
> > >> > return vmstate_save_state(f, &vmstate_virtio, vdev, NULL,
> > >> > &error_fatal);
> > >> > }
> > >> >
> > >> >+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->fd = -1;
> > >> >+ 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;
> > >> >+ }
> > >> >+
> > >> >+ /* Close file descriptor */
> > >> >+ if (mapping->fd >= 0) {
> > >> >+ close(mapping->fd);
> > >> >+ mapping->fd = -1;
> > >> >+ }
> > >> >+}
> > >> >+
> > >> >+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->fd = fd;
> > >> >+ 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)
> > >> >@@ -3212,6 +3387,7 @@ 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;
> > >> >
> > >> >@@ -3251,6 +3427,14 @@ 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,
> > >> >@@ -3574,6 +3758,7 @@ 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);
> > >> > }
> > >> >
> > >> > /*
> > >> >@@ -4085,11 +4270,24 @@ 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[] = {
> > >> >@@ -4455,9 +4653,18 @@ 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..cee807e236 100644
> > >> >--- a/include/hw/virtio/virtio.h
> > >> >+++ b/include/hw/virtio/virtio.h
> > >> >@@ -99,6 +99,46 @@ 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;
> > >> >+ int fd;
> > >> >+ 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 +208,8 @@ struct VirtIODevice
> > >> > */
> > >> > EventNotifier config_notifier;
> > >> > bool device_iotlb_enabled;
> > >> >+ /* Shared memory region for mappings. */
> > >> >+ QSIMPLEQ_HEAD(, VirtioSharedMemory) shmem_list;
> > >> > };
> > >> >
> > >> > struct VirtioDeviceClass {
> > >> >@@ -298,6 +340,100 @@ 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
> > >> >
> > >>
> > >
> >
>
