Re: [PATCH v2 07/11] vfio/migration: Implement VFIO migration protocol v2

[Joao Martins]

On 5/30/22 18:07, Avihai Horon wrote:
> +static int vfio_save_complete_precopy(QEMUFile *f, void *opaque)
> +{
> +    VFIODevice *vbasedev = opaque;
> +    enum vfio_device_mig_state recover_state;
> +    int ret;
> +
> +    /* We reach here with device state STOP or STOP_COPY only */
> +    recover_state = VFIO_DEVICE_STATE_STOP;
> +    ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_STOP_COPY,
> +                                   recover_state);
> +    if (ret) {
> +        return ret;
> +    }
> +
> +    do {
> +        ret = vfio_save_block(f, vbasedev->migration);
> +        if (ret < 0) {
> +            return ret;
> +        }
> +    } while (!ret);
> +
> +    qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
> +    ret = qemu_file_get_error(f);
> +    if (ret) {
> +        return ret;
> +    }
> +
> +    ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_STOP,
> +                                   recover_state);

Is it expected that you are setting VFIO_DEVICE_STATE_STOP while
@recover_state is the same value (VFIO_DEVICE_STATE_STOP) ?

> +    if (ret) {
> +        return ret;
> +    }
> +
> +    trace_vfio_save_complete_precopy(vbasedev->name);
> +
> +    return 0;
> +}
> +
>  static int vfio_v1_save_complete_precopy(QEMUFile *f, void *opaque)
>  {
>      VFIODevice *vbasedev = opaque;
> @@ -593,6 +775,14 @@ static void vfio_save_state(QEMUFile *f, void *opaque)
>      }
>  }
>  
> +static int vfio_load_setup(QEMUFile *f, void *opaque)
> +{
> +    VFIODevice *vbasedev = opaque;
> +
> +    return vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RESUMING,
> +                                   vbasedev->migration->device_state);
> +}
> +
>  static int vfio_v1_load_setup(QEMUFile *f, void *opaque)
>  {
>      VFIODevice *vbasedev = opaque;
> @@ -620,6 +810,15 @@ static int vfio_v1_load_setup(QEMUFile *f, void *opaque)
>      return ret;
>  }
>  
> +static int vfio_load_cleanup(void *opaque)
> +{
> +    VFIODevice *vbasedev = opaque;
> +
> +    vfio_migration_cleanup(vbasedev);
> +    trace_vfio_load_cleanup(vbasedev->name);
> +    return 0;
> +}
> +
>  static int vfio_v1_load_cleanup(void *opaque)
>  {
>      VFIODevice *vbasedev = opaque;
> @@ -662,7 +861,11 @@ static int vfio_load_state(QEMUFile *f, void *opaque, 
> int version_id)
>              uint64_t data_size = qemu_get_be64(f);
>  
>              if (data_size) {
> -                ret = vfio_v1_load_buffer(f, vbasedev, data_size);
> +                if (vbasedev->migration->v2) {
> +                    ret = vfio_load_buffer(f, vbasedev, data_size);
> +                } else {
> +                    ret = vfio_v1_load_buffer(f, vbasedev, data_size);
> +                }
>                  if (ret < 0) {
>                      return ret;
>                  }
> @@ -683,6 +886,16 @@ static int vfio_load_state(QEMUFile *f, void *opaque, 
> int version_id)
>      return ret;
>  }
>  
> +static SaveVMHandlers savevm_vfio_handlers = {
> +    .save_setup = vfio_save_setup,
> +    .save_cleanup = vfio_save_cleanup,
> +    .save_live_complete_precopy = vfio_save_complete_precopy,
> +    .save_state = vfio_save_state,
> +    .load_setup = vfio_load_setup,
> +    .load_cleanup = vfio_load_cleanup,
> +    .load_state = vfio_load_state,
> +};
> +
>  static SaveVMHandlers savevm_vfio_v1_handlers = {
>      .save_setup = vfio_v1_save_setup,
>      .save_cleanup = vfio_v1_save_cleanup,
> @@ -697,6 +910,34 @@ static SaveVMHandlers savevm_vfio_v1_handlers = {
>  
>  /* ---------------------------------------------------------------------- */
>  
> +static void vfio_vmstate_change(void *opaque, bool running, RunState state)
> +{
> +    VFIODevice *vbasedev = opaque;
> +    enum vfio_device_mig_state new_state;
> +    int ret;
> +
> +    if (running) {
> +        new_state = VFIO_DEVICE_STATE_RUNNING;
> +    } else {
> +        new_state = VFIO_DEVICE_STATE_STOP;
> +    }
> +
> +    ret = vfio_migration_set_state(vbasedev, new_state,
> +                                   VFIO_DEVICE_STATE_ERROR);
> +    if (ret) {
> +        /*
> +         * Migration should be aborted in this case, but vm_state_notify()
> +         * currently does not support reporting failures.
> +         */
> +        if (migrate_get_current()->to_dst_file) {
> +            qemu_file_set_error(migrate_get_current()->to_dst_file, ret);
> +        }
> +    }
> +
> +    trace_vfio_vmstate_change(vbasedev->name, running, RunState_str(state),
> +                              new_state);
> +}
> +
>  static void vfio_v1_vmstate_change(void *opaque, bool running, RunState 
> state)
>  {
>      VFIODevice *vbasedev = opaque;
> @@ -770,12 +1011,17 @@ static void vfio_migration_state_notifier(Notifier 
> *notifier, void *data)
>      case MIGRATION_STATUS_CANCELLED:
>      case MIGRATION_STATUS_FAILED:
>          bytes_transferred = 0;
> -        ret = vfio_migration_v1_set_state(vbasedev,
> -                                          ~(VFIO_DEVICE_STATE_V1_SAVING |
> -                                            VFIO_DEVICE_STATE_V1_RESUMING),
> -                                          VFIO_DEVICE_STATE_V1_RUNNING);
> -        if (ret) {
> -            error_report("%s: Failed to set state RUNNING", vbasedev->name);
> +        if (migration->v2) {
> +            vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RUNNING,
> +                                     VFIO_DEVICE_STATE_ERROR);

Perhaps you are discarding the error?

Shouldn't it be:

        err =  vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RUNNING,
                                        VFIO_DEVICE_STATE_ERROR);

> +        } else {
> +            ret = vfio_migration_v1_set_state(vbasedev,
> +                                              ~(VFIO_DEVICE_STATE_V1_SAVING |
> +                                                
> VFIO_DEVICE_STATE_V1_RESUMING),
> +                                              VFIO_DEVICE_STATE_V1_RUNNING);
> +            if (ret) {
> +                error_report("%s: Failed to set state RUNNING", 
> vbasedev->name);
> +            }

Perhaps this error_report and condition is in the wrong scope?

Shouldn't it be more like this:

if (migration->v2) {
        ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RUNNING,
                                 VFIO_DEVICE_STATE_ERROR);
} else {
        ret = vfio_migration_v1_set_state(vbasedev,
                                          ~(VFIO_DEVICE_STATE_V1_SAVING |
                                            VFIO_DEVICE_STATE_V1_RESUMING),
                                          VFIO_DEVICE_STATE_V1_RUNNING);
}


if (ret) {
    error_report("%s: Failed to set state RUNNING", vbasedev->name);
}

>          }
>      }
>  }
> @@ -784,12 +1030,35 @@ static void vfio_migration_exit(VFIODevice *vbasedev)
>  {
>      VFIOMigration *migration = vbasedev->migration;
>  
> -    vfio_region_exit(&migration->region);
> -    vfio_region_finalize(&migration->region);
> +    if (migration->v2) {
> +        g_free(migration->data_buffer);
> +    } else {
> +        vfio_region_exit(&migration->region);
> +        vfio_region_finalize(&migration->region);
> +    }
>      g_free(vbasedev->migration);
>      vbasedev->migration = NULL;
>  }
>  
> +static int vfio_migration_query_flags(VFIODevice *vbasedev, uint64_t 
> *mig_flags)
> +{
> +    uint64_t buf[DIV_ROUND_UP(sizeof(struct vfio_device_feature) +
> +                                  sizeof(struct 
> vfio_device_feature_migration),
> +                              sizeof(uint64_t))] = {};
> +    struct vfio_device_feature *feature = (void *)buf;
> +    struct vfio_device_feature_migration *mig = (void *)feature->data;
> +
> +    feature->argsz = sizeof(buf);
> +    feature->flags = VFIO_DEVICE_FEATURE_GET | VFIO_DEVICE_FEATURE_MIGRATION;
> +    if (ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature)) {
> +        return -EOPNOTSUPP;
> +    }
> +
> +    *mig_flags = mig->flags;
> +
> +    return 0;
> +}
> +
>  static int vfio_migration_init(VFIODevice *vbasedev)
>  {
>      int ret;
> @@ -798,6 +1067,7 @@ static int vfio_migration_init(VFIODevice *vbasedev)
>      char id[256] = "";
>      g_autofree char *path = NULL, *oid = NULL;
>      struct vfio_region_info *info = NULL;
> +    uint64_t mig_flags;
>  
>      if (!vbasedev->ops->vfio_get_object) {
>          return -EINVAL;
> @@ -808,32 +1078,48 @@ static int vfio_migration_init(VFIODevice *vbasedev)
>          return -EINVAL;
>      }
>  
> -    ret = vfio_get_dev_region_info(vbasedev,
> -                                   VFIO_REGION_TYPE_MIGRATION_DEPRECATED,
> -                                   VFIO_REGION_SUBTYPE_MIGRATION_DEPRECATED,
> -                                   &info);
> -    if (ret) {
> -        return ret;
> -    }
> +    ret = vfio_migration_query_flags(vbasedev, &mig_flags);
> +    if (!ret) {
> +        /* Migration v2 */
> +        /* Basic migration functionality must be supported */
> +        if (!(mig_flags & VFIO_MIGRATION_STOP_COPY)) {
> +            return -EOPNOTSUPP;
> +        }
> +        vbasedev->migration = g_new0(VFIOMigration, 1);
> +        vbasedev->migration->data_buffer_size = VFIO_MIG_DATA_BUFFER_SIZE;
> +        vbasedev->migration->data_buffer =
> +            g_malloc0(vbasedev->migration->data_buffer_size);
> +        vbasedev->migration->data_fd = -1;
> +        vbasedev->migration->v2 = true;
> +    } else {
> +        /* Migration v1 */
> +        ret = vfio_get_dev_region_info(vbasedev,
> +                                       VFIO_REGION_TYPE_MIGRATION_DEPRECATED,
> +                                       
> VFIO_REGION_SUBTYPE_MIGRATION_DEPRECATED,
> +                                       &info);
> +        if (ret) {
> +            return ret;
> +        }
>  
> -    vbasedev->migration = g_new0(VFIOMigration, 1);
> +        vbasedev->migration = g_new0(VFIOMigration, 1);
>  
> -    ret = vfio_region_setup(obj, vbasedev, &vbasedev->migration->region,
> -                            info->index, "migration");
> -    if (ret) {
> -        error_report("%s: Failed to setup VFIO migration region %d: %s",
> -                     vbasedev->name, info->index, strerror(-ret));
> -        goto err;
> -    }
> +        ret = vfio_region_setup(obj, vbasedev, &vbasedev->migration->region,
> +                                info->index, "migration");
> +        if (ret) {
> +            error_report("%s: Failed to setup VFIO migration region %d: %s",
> +                         vbasedev->name, info->index, strerror(-ret));
> +            goto err;
> +        }
>  
> -    if (!vbasedev->migration->region.size) {
> -        error_report("%s: Invalid zero-sized VFIO migration region %d",
> -                     vbasedev->name, info->index);
> -        ret = -EINVAL;
> -        goto err;
> -    }
> +        if (!vbasedev->migration->region.size) {
> +            error_report("%s: Invalid zero-sized VFIO migration region %d",
> +                         vbasedev->name, info->index);
> +            ret = -EINVAL;
> +            goto err;
> +        }
>  
> -    g_free(info);
> +        g_free(info);
> +    }
>  
>      migration = vbasedev->migration;
>      migration->vbasedev = vbasedev;
> @@ -846,11 +1132,20 @@ static int vfio_migration_init(VFIODevice *vbasedev)
>      }
>      strpadcpy(id, sizeof(id), path, '\0');
>  
> -    register_savevm_live(id, VMSTATE_INSTANCE_ID_ANY, 1,
> -                         &savevm_vfio_v1_handlers, vbasedev);
> +    if (migration->v2) {
> +        register_savevm_live(id, VMSTATE_INSTANCE_ID_ANY, 1,
> +                             &savevm_vfio_handlers, vbasedev);
> +
> +        migration->vm_state = qdev_add_vm_change_state_handler(
> +            vbasedev->dev, vfio_vmstate_change, vbasedev);
> +    } else {
> +        register_savevm_live(id, VMSTATE_INSTANCE_ID_ANY, 1,
> +                             &savevm_vfio_v1_handlers, vbasedev);
> +
> +        migration->vm_state = qdev_add_vm_change_state_handler(
> +            vbasedev->dev, vfio_v1_vmstate_change, vbasedev);
> +    }
>  
> -    migration->vm_state = qdev_add_vm_change_state_handler(
> -        vbasedev->dev, vfio_v1_vmstate_change, vbasedev);
>      migration->migration_state.notify = vfio_migration_state_notifier;
>      add_migration_state_change_notifier(&migration->migration_state);
>      return 0;
> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
> index ac8b04f52a..6e8c5958b9 100644
> --- a/hw/vfio/trace-events
> +++ b/hw/vfio/trace-events
> @@ -163,6 +163,8 @@ vfio_save_complete_precopy(const char *name) " (%s)"
>  vfio_load_device_config_state(const char *name) " (%s)"
>  vfio_load_state(const char *name, uint64_t data) " (%s) data 0x%"PRIx64
>  vfio_v1_load_state_device_data(const char *name, uint64_t data_offset, 
> uint64_t data_size) " (%s) Offset 0x%"PRIx64" size 0x%"PRIx64
> +vfio_load_state_device_data(const char *name, uint64_t data_size) " (%s) 
> size 0x%"PRIx64
>  vfio_load_cleanup(const char *name) " (%s)"
>  vfio_get_dirty_bitmap(int fd, uint64_t iova, uint64_t size, uint64_t 
> bitmap_size, uint64_t start) "container fd=%d, iova=0x%"PRIx64" size= 
> 0x%"PRIx64" bitmap_size=0x%"PRIx64" start=0x%"PRIx64
>  vfio_iommu_map_dirty_notify(uint64_t iova_start, uint64_t iova_end) "iommu 
> dirty @ 0x%"PRIx64" - 0x%"PRIx64
> +vfio_save_block(const char *name, int data_size) " (%s) data_size %d"
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index bbaf72ba00..2ec3346fea 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -66,6 +66,11 @@ typedef struct VFIOMigration {
>      int vm_running;
>      Notifier migration_state;
>      uint64_t pending_bytes;
> +    enum vfio_device_mig_state device_state;
> +    int data_fd;
> +    void *data_buffer;
> +    size_t data_buffer_size;
> +    bool v2;
>  } VFIOMigration;
>  
>  typedef struct VFIOAddressSpace {