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Re: [PATCH v6 17/19] vfio-user: register handlers to facilitate migratio


From: Paolo Bonzini
Subject: Re: [PATCH v6 17/19] vfio-user: register handlers to facilitate migration
Date: Fri, 18 Feb 2022 13:20:37 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0

On 2/17/22 08:49, Jagannathan Raman wrote:
Store and load the device's state during migration. use libvfio-user's
handlers for this purpose

Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Signed-off-by: John G Johnson <john.g.johnson@oracle.com>
Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>

Why does no one call clear_deferred_backend_init?

Paolo

---
  include/block/block.h       |   1 +
  include/migration/vmstate.h |   2 +
  migration/savevm.h          |   2 +
  block.c                     |   5 +
  hw/remote/machine.c         |   7 +
  hw/remote/vfio-user-obj.c   | 467 ++++++++++++++++++++++++++++++++++++
  migration/savevm.c          |  89 +++++++
  migration/vmstate.c         |  19 ++
  8 files changed, 592 insertions(+)

diff --git a/include/block/block.h b/include/block/block.h
index e1713ee306..02b89e0668 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -495,6 +495,7 @@ int generated_co_wrapper 
bdrv_invalidate_cache(BlockDriverState *bs,
                                                 Error **errp);
  void bdrv_invalidate_cache_all(Error **errp);
  int bdrv_inactivate_all(void);
+int bdrv_inactivate(BlockDriverState *bs);
/* Ensure contents are flushed to disk. */
  int generated_co_wrapper bdrv_flush(BlockDriverState *bs);
diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 017c03675c..68bea576ea 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -1165,6 +1165,8 @@ extern const VMStateInfo vmstate_info_qlist;
  #define VMSTATE_END_OF_LIST()                                         \
      {}
+uint64_t vmstate_vmsd_size(PCIDevice *pci_dev);
+
  int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd,
                         void *opaque, int version_id);
  int vmstate_save_state(QEMUFile *f, const VMStateDescription *vmsd,
diff --git a/migration/savevm.h b/migration/savevm.h
index 6461342cb4..8007064ff2 100644
--- a/migration/savevm.h
+++ b/migration/savevm.h
@@ -67,5 +67,7 @@ int qemu_loadvm_state_main(QEMUFile *f, 
MigrationIncomingState *mis);
  int qemu_load_device_state(QEMUFile *f);
  int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
          bool in_postcopy, bool inactivate_disks);
+int qemu_remote_savevm(QEMUFile *f, DeviceState *dev);
+int qemu_remote_loadvm(QEMUFile *f);
#endif
diff --git a/block.c b/block.c
index b54d59d1fa..e90aaee30c 100644
--- a/block.c
+++ b/block.c
@@ -6565,6 +6565,11 @@ static int bdrv_inactivate_recurse(BlockDriverState *bs)
      return 0;
  }
+int bdrv_inactivate(BlockDriverState *bs)
+{
+    return bdrv_inactivate_recurse(bs);
+}
+
  int bdrv_inactivate_all(void)
  {
      BlockDriverState *bs = NULL;
diff --git a/hw/remote/machine.c b/hw/remote/machine.c
index a8b4a3aef3..31ef401e43 100644
--- a/hw/remote/machine.c
+++ b/hw/remote/machine.c
@@ -24,6 +24,7 @@
  #include "hw/qdev-core.h"
  #include "hw/remote/iommu.h"
  #include "hw/remote/vfio-user-obj.h"
+#include "sysemu/sysemu.h"
static void remote_machine_init(MachineState *machine)
  {
@@ -86,6 +87,11 @@ static void remote_machine_set_vfio_user(Object *obj, bool 
value, Error **errp)
      s->vfio_user = value;
  }
+static void remote_machine_instance_init(Object *obj)
+{
+    set_deferred_backend_init();
+}
+
  static void remote_machine_class_init(ObjectClass *oc, void *data)
  {
      MachineClass *mc = MACHINE_CLASS(oc);
@@ -105,6 +111,7 @@ static const TypeInfo remote_machine = {
      .name = TYPE_REMOTE_MACHINE,
      .parent = TYPE_MACHINE,
      .instance_size = sizeof(RemoteMachineState),
+    .instance_init = remote_machine_instance_init,
      .class_init = remote_machine_class_init,
      .interfaces = (InterfaceInfo[]) {
          { TYPE_HOTPLUG_HANDLER },
diff --git a/hw/remote/vfio-user-obj.c b/hw/remote/vfio-user-obj.c
index d79bab87f1..2304643003 100644
--- a/hw/remote/vfio-user-obj.c
+++ b/hw/remote/vfio-user-obj.c
@@ -57,6 +57,13 @@
  #include "hw/pci/msi.h"
  #include "hw/pci/msix.h"
  #include "hw/remote/vfio-user-obj.h"
+#include "migration/qemu-file.h"
+#include "migration/savevm.h"
+#include "migration/vmstate.h"
+#include "migration/global_state.h"
+#include "block/block.h"
+#include "sysemu/block-backend.h"
+#include "net/net.h"
#define TYPE_VFU_OBJECT "x-vfio-user-server"
  OBJECT_DECLARE_TYPE(VfuObject, VfuObjectClass, VFU_OBJECT)
@@ -108,12 +115,49 @@ struct VfuObject {
      Error *unplug_blocker;
int vfu_poll_fd;
+
+    /*
+     * vfu_mig_buf holds the migration data. In the remote server, this
+     * buffer replaces the role of an IO channel which links the source
+     * and the destination.
+     *
+     * Whenever the client QEMU process initiates migration, the remote
+     * server gets notified via libvfio-user callbacks. The remote server
+     * sets up a QEMUFile object using this buffer as backend. The remote
+     * server passes this object to its migration subsystem, which slurps
+     * the VMSD of the device ('devid' above) referenced by this object
+     * and stores the VMSD in this buffer.
+     *
+     * The client subsequetly asks the remote server for any data that
+     * needs to be moved over to the destination via libvfio-user
+     * library's vfu_migration_callbacks_t callbacks. The remote hands
+     * over this buffer as data at this time.
+     *
+     * A reverse of this process happens at the destination.
+     */
+    uint8_t *vfu_mig_buf;
+
+    uint64_t vfu_mig_buf_size;
+
+    uint64_t vfu_mig_buf_pending;
+
+    uint64_t vfu_mig_data_written;
+
+    uint64_t vfu_mig_section_offset;
+
+    QEMUFile *vfu_mig_file;
+
+    vfu_migr_state_t vfu_state;
  };
static GHashTable *vfu_object_bdf_to_ctx_table; #define INT2VOIDP(i) (void *)(uintptr_t)(i) +#define KB(x) ((size_t) (x) << 10)
+
+#define VFU_OBJECT_MIG_WINDOW KB(64)
+
  static void vfu_object_init_ctx(VfuObject *o, Error **errp);
static void vfu_object_set_socket(Object *obj, Visitor *v, const char *name,
@@ -163,6 +207,394 @@ static void vfu_object_set_device(Object *obj, const char 
*str, Error **errp)
      vfu_object_init_ctx(o, errp);
  }
+/**
+ * Migration helper functions
+ *
+ * vfu_mig_buf_read & vfu_mig_buf_write are used by QEMU's migration
+ * subsystem - qemu_remote_loadvm & qemu_remote_savevm. loadvm/savevm
+ * call these functions via QEMUFileOps to load/save the VMSD of a
+ * device into vfu_mig_buf
+ *
+ */
+static ssize_t vfu_mig_buf_read(void *opaque, uint8_t *buf, int64_t pos,
+                                size_t size, Error **errp)
+{
+    VfuObject *o = opaque;
+
+    if (pos > o->vfu_mig_buf_size) {
+        size = 0;
+    } else if ((pos + size) > o->vfu_mig_buf_size) {
+        size = o->vfu_mig_buf_size - pos;
+    }
+
+    memcpy(buf, (o->vfu_mig_buf + pos), size);
+
+    return size;
+}
+
+static ssize_t vfu_mig_buf_write(void *opaque, struct iovec *iov, int iovcnt,
+                                 int64_t pos, Error **errp)
+{
+    ERRP_GUARD();
+    VfuObject *o = opaque;
+    uint64_t end = pos + iov_size(iov, iovcnt);
+    int i;
+
+    if (o->vfu_mig_buf_pending) {
+        error_setg(errp, "Migration is ongoing");
+        return 0;
+    }
+
+    if (end > o->vfu_mig_buf_size) {
+        o->vfu_mig_buf = g_realloc(o->vfu_mig_buf, end);
+    }
+
+    for (i = 0; i < iovcnt; i++) {
+        memcpy((o->vfu_mig_buf + o->vfu_mig_buf_size), iov[i].iov_base,
+               iov[i].iov_len);
+        o->vfu_mig_buf_size += iov[i].iov_len;
+    }
+
+    return iov_size(iov, iovcnt);
+}
+
+static int vfu_mig_buf_shutdown(void *opaque, bool rd, bool wr, Error **errp)
+{
+    VfuObject *o = opaque;
+
+    o->vfu_mig_buf_size = 0;
+
+    g_free(o->vfu_mig_buf);
+
+    o->vfu_mig_buf = NULL;
+
+    o->vfu_mig_buf_pending = 0;
+
+    o->vfu_mig_data_written = 0;
+
+    o->vfu_mig_section_offset = 0;
+
+    return 0;
+}
+
+static const QEMUFileOps vfu_mig_fops_save = {
+    .writev_buffer  = vfu_mig_buf_write,
+    .shut_down      = vfu_mig_buf_shutdown,
+};
+
+static const QEMUFileOps vfu_mig_fops_load = {
+    .get_buffer     = vfu_mig_buf_read,
+    .shut_down      = vfu_mig_buf_shutdown,
+};
+
+static BlockDriverState *vfu_object_find_bs_by_dev(DeviceState *dev)
+{
+    BlockBackend *blk = blk_by_dev(dev);
+
+    if (!blk) {
+        return NULL;
+    }
+
+    return blk_bs(blk);
+}
+
+static int vfu_object_bdrv_invalidate_cache_by_dev(DeviceState *dev)
+{
+    BlockDriverState *bs = NULL;
+    Error *local_err = NULL;
+
+    bs = vfu_object_find_bs_by_dev(dev);
+    if (!bs) {
+        return 0;
+    }
+
+    bdrv_invalidate_cache(bs, &local_err);
+    if (local_err) {
+        error_report_err(local_err);
+        return -1;
+    }
+
+    return 0;
+}
+
+static int vfu_object_bdrv_inactivate_by_dev(DeviceState *dev)
+{
+    BlockDriverState *bs = NULL;
+
+    bs = vfu_object_find_bs_by_dev(dev);
+    if (!bs) {
+        return 0;
+    }
+
+    return bdrv_inactivate(bs);
+}
+
+static void vfu_object_start_stop_netdev(DeviceState *dev, bool start)
+{
+    NetClientState *nc = NULL;
+    Error *local_err = NULL;
+    char *netdev = NULL;
+
+    netdev = object_property_get_str(OBJECT(dev), "netdev", &local_err);
+    if (local_err) {
+        /**
+         * object_property_get_str() sets Error if netdev property is
+         * not found, not necessarily an error in the context of
+         * this function
+         */
+        error_free(local_err);
+        return;
+    }
+
+    if (!netdev) {
+        return;
+    }
+
+    nc = qemu_find_netdev(netdev);
+
+    if (!nc) {
+        return;
+    }
+
+    if (!start) {
+        qemu_flush_or_purge_queued_packets(nc, true);
+
+        if (nc->info && nc->info->cleanup) {
+            nc->info->cleanup(nc);
+        }
+    } else if (nc->peer) {
+        qemu_flush_or_purge_queued_packets(nc->peer, false);
+    }
+}
+
+static int vfu_object_start_devs(DeviceState *dev, void *opaque)
+{
+    int ret = vfu_object_bdrv_invalidate_cache_by_dev(dev);
+
+    if (ret) {
+        return ret;
+    }
+
+    vfu_object_start_stop_netdev(dev, true);
+
+    return ret;
+}
+
+static int vfu_object_stop_devs(DeviceState *dev, void *opaque)
+{
+    int ret = vfu_object_bdrv_inactivate_by_dev(dev);
+
+    if (ret) {
+        return ret;
+    }
+
+    vfu_object_start_stop_netdev(dev, false);
+
+    return ret;
+}
+
+/**
+ * handlers for vfu_migration_callbacks_t
+ *
+ * The libvfio-user library accesses these handlers to drive the migration
+ * at the remote end, and also to transport the data stored in vfu_mig_buf
+ *
+ */
+static void vfu_mig_state_stop_and_copy(vfu_ctx_t *vfu_ctx)
+{
+    VfuObject *o = vfu_get_private(vfu_ctx);
+    int ret;
+
+    if (!o->vfu_mig_file) {
+        o->vfu_mig_file = qemu_fopen_ops(o, &vfu_mig_fops_save, false);
+    }
+
+    ret = qemu_remote_savevm(o->vfu_mig_file, DEVICE(o->pci_dev));
+    if (ret) {
+        qemu_file_shutdown(o->vfu_mig_file);
+        o->vfu_mig_file = NULL;
+        return;
+    }
+
+    qemu_fflush(o->vfu_mig_file);
+}
+
+static void vfu_mig_state_running(vfu_ctx_t *vfu_ctx)
+{
+    VfuObject *o = vfu_get_private(vfu_ctx);
+    int ret;
+
+    if (o->vfu_state != VFU_MIGR_STATE_RESUME) {
+        goto run_ctx;
+    }
+
+    if (!o->vfu_mig_file) {
+        o->vfu_mig_file = qemu_fopen_ops(o, &vfu_mig_fops_load, false);
+    }
+
+    ret = qemu_remote_loadvm(o->vfu_mig_file);
+    if (ret) {
+        VFU_OBJECT_ERROR(o, "vfu: failed to restore device state");
+        return;
+    }
+
+    qemu_file_shutdown(o->vfu_mig_file);
+    o->vfu_mig_file = NULL;
+
+run_ctx:
+    ret = qdev_walk_children(DEVICE(o->pci_dev), NULL, NULL,
+                             vfu_object_start_devs,
+                             NULL, NULL);
+    if (ret) {
+        VFU_OBJECT_ERROR(o, "vfu: failed to setup backends for %s",
+                         o->device);
+        return;
+    }
+}
+
+static void vfu_mig_state_stop(vfu_ctx_t *vfu_ctx)
+{
+    VfuObject *o = vfu_get_private(vfu_ctx);
+    int ret;
+
+    ret = qdev_walk_children(DEVICE(o->pci_dev), NULL, NULL,
+                             vfu_object_stop_devs,
+                             NULL, NULL);
+    if (ret) {
+        VFU_OBJECT_ERROR(o, "vfu: failed to inactivate backends for %s",
+                         o->device);
+    }
+}
+
+static int vfu_mig_transition(vfu_ctx_t *vfu_ctx, vfu_migr_state_t state)
+{
+    VfuObject *o = vfu_get_private(vfu_ctx);
+
+    if (o->vfu_state == state) {
+        return 0;
+    }
+
+    switch (state) {
+    case VFU_MIGR_STATE_RESUME:
+        break;
+    case VFU_MIGR_STATE_STOP_AND_COPY:
+        vfu_mig_state_stop_and_copy(vfu_ctx);
+        break;
+    case VFU_MIGR_STATE_STOP:
+        vfu_mig_state_stop(vfu_ctx);
+        break;
+    case VFU_MIGR_STATE_PRE_COPY:
+        break;
+    case VFU_MIGR_STATE_RUNNING:
+        vfu_mig_state_running(vfu_ctx);
+        break;
+    default:
+        warn_report("vfu: Unknown migration state %d", state);
+    }
+
+    o->vfu_state = state;
+
+    return 0;
+}
+
+static uint64_t vfu_mig_get_pending_bytes(vfu_ctx_t *vfu_ctx)
+{
+    VfuObject *o = vfu_get_private(vfu_ctx);
+    static bool mig_ongoing;
+
+    if (!mig_ongoing && !o->vfu_mig_buf_pending) {
+        o->vfu_mig_buf_pending = o->vfu_mig_buf_size;
+        mig_ongoing = true;
+    }
+
+    if (mig_ongoing && !o->vfu_mig_buf_pending) {
+        mig_ongoing = false;
+    }
+
+    return o->vfu_mig_buf_pending;
+}
+
+static int vfu_mig_prepare_data(vfu_ctx_t *vfu_ctx, uint64_t *offset,
+                                uint64_t *size)
+{
+    VfuObject *o = vfu_get_private(vfu_ctx);
+    uint64_t data_size = o->vfu_mig_buf_pending;
+
+    if (data_size > VFU_OBJECT_MIG_WINDOW) {
+        data_size = VFU_OBJECT_MIG_WINDOW;
+    }
+
+    o->vfu_mig_section_offset = o->vfu_mig_buf_size - o->vfu_mig_buf_pending;
+
+    o->vfu_mig_buf_pending -= data_size;
+
+    if (offset) {
+        *offset = 0;
+    }
+
+    if (size) {
+        *size = data_size;
+    }
+
+    return 0;
+}
+
+static ssize_t vfu_mig_read_data(vfu_ctx_t *vfu_ctx, void *buf,
+                                 uint64_t size, uint64_t offset)
+{
+    VfuObject *o = vfu_get_private(vfu_ctx);
+    uint64_t read_offset = o->vfu_mig_section_offset + offset;
+
+    if (read_offset > o->vfu_mig_buf_size) {
+        warn_report("vfu: buffer overflow - offset outside range");
+        return -1;
+    }
+
+    if ((read_offset + size) > o->vfu_mig_buf_size) {
+        warn_report("vfu: buffer overflow - size outside range");
+        size = o->vfu_mig_buf_size - read_offset;
+    }
+
+    memcpy(buf, (o->vfu_mig_buf + read_offset), size);
+
+    return size;
+}
+
+static ssize_t vfu_mig_write_data(vfu_ctx_t *vfu_ctx, void *data,
+                                  uint64_t size, uint64_t offset)
+{
+    VfuObject *o = vfu_get_private(vfu_ctx);
+    uint64_t end = o->vfu_mig_data_written + offset + size;
+
+    if (end > o->vfu_mig_buf_size) {
+        o->vfu_mig_buf = g_realloc(o->vfu_mig_buf, end);
+        o->vfu_mig_buf_size = end;
+    }
+
+    memcpy((o->vfu_mig_buf + o->vfu_mig_data_written + offset), data, size);
+
+    return size;
+}
+
+static int vfu_mig_data_written(vfu_ctx_t *vfu_ctx, uint64_t count)
+{
+    VfuObject *o = vfu_get_private(vfu_ctx);
+
+    o->vfu_mig_data_written += count;
+
+    return 0;
+}
+
+static const vfu_migration_callbacks_t vfu_mig_cbs = {
+    .version = VFU_MIGR_CALLBACKS_VERS,
+    .transition = &vfu_mig_transition,
+    .get_pending_bytes = &vfu_mig_get_pending_bytes,
+    .prepare_data = &vfu_mig_prepare_data,
+    .read_data = &vfu_mig_read_data,
+    .data_written = &vfu_mig_data_written,
+    .write_data = &vfu_mig_write_data,
+};
+
  static void vfu_object_ctx_run(void *opaque)
  {
      VfuObject *o = opaque;
@@ -550,6 +982,13 @@ void vfu_object_set_bus_irq(PCIBus *pci_bus)
      pci_bus_irqs(pci_bus, vfu_object_set_irq, vfu_object_map_irq, NULL, 1);
  }
+static bool vfu_object_migratable(VfuObject *o)
+{
+    DeviceClass *dc = DEVICE_GET_CLASS(o->pci_dev);
+
+    return dc->vmsd && !dc->vmsd->unmigratable;
+}
+
  /*
   * TYPE_VFU_OBJECT depends on the availability of the 'socket' and 'device'
   * properties. It also depends on devices instantiated in QEMU. These
@@ -575,6 +1014,7 @@ static void vfu_object_init_ctx(VfuObject *o, Error **errp)
      ERRP_GUARD();
      DeviceState *dev = NULL;
      vfu_pci_type_t pci_type = VFU_PCI_TYPE_CONVENTIONAL;
+    uint64_t migr_regs_size, migr_size;
      int ret;
if (o->vfu_ctx || !o->socket || !o->device ||
@@ -653,6 +1093,31 @@ static void vfu_object_init_ctx(VfuObject *o, Error 
**errp)
          goto fail;
      }
+ migr_regs_size = vfu_get_migr_register_area_size();
+    migr_size = migr_regs_size + VFU_OBJECT_MIG_WINDOW;
+
+    ret = vfu_setup_region(o->vfu_ctx, VFU_PCI_DEV_MIGR_REGION_IDX,
+                           migr_size, NULL,
+                           VFU_REGION_FLAG_RW, NULL, 0, -1, 0);
+    if (ret < 0) {
+        error_setg(errp, "vfu: Failed to register migration BAR %s- %s",
+                   o->device, strerror(errno));
+        goto fail;
+    }
+
+    if (!vfu_object_migratable(o)) {
+        goto realize_ctx;
+    }
+
+    ret = vfu_setup_device_migration_callbacks(o->vfu_ctx, &vfu_mig_cbs,
+                                               migr_regs_size);
+    if (ret < 0) {
+        error_setg(errp, "vfu: Failed to setup migration %s- %s",
+                   o->device, strerror(errno));
+        goto fail;
+    }
+
+realize_ctx:
      ret = vfu_realize_ctx(o->vfu_ctx);
      if (ret < 0) {
          error_setg(errp, "vfu: Failed to realize device %s- %s",
@@ -700,6 +1165,8 @@ static void vfu_object_init(Object *obj)
      }
o->vfu_poll_fd = -1;
+
+    o->vfu_state = VFU_MIGR_STATE_STOP;
  }
static void vfu_object_finalize(Object *obj)
diff --git a/migration/savevm.c b/migration/savevm.c
index 1599b02fbc..2cc3b74287 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -66,6 +66,7 @@
  #include "net/announce.h"
  #include "qemu/yank.h"
  #include "yank_functions.h"
+#include "hw/qdev-core.h"
const unsigned int postcopy_ram_discard_version; @@ -1606,6 +1607,64 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
      return ret;
  }
+static SaveStateEntry *find_se_from_dev(DeviceState *dev)
+{
+    SaveStateEntry *se;
+
+    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
+        if (se->opaque == dev) {
+            return se;
+        }
+    }
+
+    return NULL;
+}
+
+static int qemu_remote_savevm_section_full(DeviceState *dev, void *opaque)
+{
+    QEMUFile *f = opaque;
+    SaveStateEntry *se;
+    int ret;
+
+    se = find_se_from_dev(dev);
+    if (!se) {
+        return 0;
+    }
+
+    if (!se->vmsd || !vmstate_save_needed(se->vmsd, se->opaque) ||
+        se->vmsd->unmigratable) {
+        return 0;
+    }
+
+    save_section_header(f, se, QEMU_VM_SECTION_FULL);
+
+    ret = vmstate_save(f, se, NULL);
+    if (ret) {
+        qemu_file_set_error(f, ret);
+        return ret;
+    }
+
+    save_section_footer(f, se);
+
+    return 0;
+}
+
+int qemu_remote_savevm(QEMUFile *f, DeviceState *dev)
+{
+    int ret = qdev_walk_children(dev, NULL, NULL,
+                                 qemu_remote_savevm_section_full,
+                                 NULL, f);
+
+    if (ret) {
+        return ret;
+    }
+
+    qemu_put_byte(f, QEMU_VM_EOF);
+    qemu_fflush(f);
+
+    return 0;
+}
+
  void qemu_savevm_live_state(QEMUFile *f)
  {
      /* save QEMU_VM_SECTION_END section */
@@ -2447,6 +2506,36 @@ qemu_loadvm_section_start_full(QEMUFile *f, 
MigrationIncomingState *mis)
      return 0;
  }
+int qemu_remote_loadvm(QEMUFile *f)
+{
+    uint8_t section_type;
+    int ret = 0;
+
+    while (true) {
+        section_type = qemu_get_byte(f);
+
+        ret = qemu_file_get_error(f);
+        if (ret) {
+            break;
+        }
+
+        switch (section_type) {
+        case QEMU_VM_SECTION_FULL:
+            ret = qemu_loadvm_section_start_full(f, NULL);
+            if (ret < 0) {
+                break;
+            }
+            break;
+        case QEMU_VM_EOF:
+            return ret;
+        default:
+            return -EINVAL;
+        }
+    }
+
+    return ret;
+}
+
  static int
  qemu_loadvm_section_part_end(QEMUFile *f, MigrationIncomingState *mis)
  {
diff --git a/migration/vmstate.c b/migration/vmstate.c
index 05f87cdddc..83f8562792 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -63,6 +63,25 @@ static int vmstate_size(void *opaque, const VMStateField 
*field)
      return size;
  }
+uint64_t vmstate_vmsd_size(PCIDevice *pci_dev)
+{
+    DeviceClass *dc = DEVICE_GET_CLASS(DEVICE(pci_dev));
+    const VMStateField *field = NULL;
+    uint64_t size = 0;
+
+    if (!dc->vmsd) {
+        return 0;
+    }
+
+    field = dc->vmsd->fields;
+    while (field && field->name) {
+        size += vmstate_size(pci_dev, field);
+        field++;
+    }
+
+    return size;
+}
+
  static void vmstate_handle_alloc(void *ptr, const VMStateField *field,
                                   void *opaque)
  {




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