Re: [PATCH v4 19/25] vfio: Use new Error** argument in vfio_save_setup()

[Eric Auger]

Hi Cédric,

On 3/6/24 14:34, Cédric Le Goater wrote:
> Add an Error** argument to vfio_migration_set_state() and adjust
> callers, including vfio_save_setup(). The error will be propagated up
> to qemu_savevm_state_setup() where the save_setup() handler is
> executed.
> 
> Modify vfio_vmstate_change_prepare() and vfio_vmstate_change() to
> store a reported error under the migration stream if a migration is in
> progress.
> 
> Signed-off-by: Cédric Le Goater <clg@redhat.com>
> ---
> 
>  Changes in v3:
> 
>  - Use error_setg_errno() in vfio_save_setup() 
>  - Made sure an error is always set in case of failure in
>    vfio_load_setup()
>    
>  hw/vfio/migration.c | 67 ++++++++++++++++++++++++++-------------------
>  1 file changed, 39 insertions(+), 28 deletions(-)
> 
> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> index 
> a3bb1a92ba0b9c2c585efe54cfda0b774a81dcb9..71ade14a7942358094371a86c00718f5979113ea
>  100644
> --- a/hw/vfio/migration.c
> +++ b/hw/vfio/migration.c
> @@ -84,7 +84,8 @@ static const char *mig_state_to_str(enum 
> vfio_device_mig_state state)
>  
>  static int vfio_migration_set_state(VFIODevice *vbasedev,
>                                      enum vfio_device_mig_state new_state,
> -                                    enum vfio_device_mig_state recover_state)
> +                                    enum vfio_device_mig_state recover_state,
> +                                    Error **errp)
>  {
>      VFIOMigration *migration = vbasedev->migration;
>      uint64_t buf[DIV_ROUND_UP(sizeof(struct vfio_device_feature) +
> @@ -104,15 +105,15 @@ static int vfio_migration_set_state(VFIODevice 
> *vbasedev,
>          ret = -errno;
>  
>          if (recover_state == VFIO_DEVICE_STATE_ERROR) {
> -            error_report("%s: Failed setting device state to %s, err: %s. "
> -                         "Recover state is ERROR. Resetting device",
> -                         vbasedev->name, mig_state_to_str(new_state),
> -                         strerror(errno));
> +            error_setg(errp, "%s: Failed setting device state to %s, err: 
> %s. "
> +                       "Recover state is ERROR. Resetting device",
> +                       vbasedev->name, mig_state_to_str(new_state),
> +                       strerror(errno));
you can use the error_setg_errno variant here and below.
>  
>              goto reset_device;
>          }
>  
> -        error_report(
> +        error_setg(errp,
>              "%s: Failed setting device state to %s, err: %s. Setting device 
> in recover state %s",
>                       vbasedev->name, mig_state_to_str(new_state),
>                       strerror(errno), mig_state_to_str(recover_state));
> @@ -120,7 +121,7 @@ static int vfio_migration_set_state(VFIODevice *vbasedev,
>          mig_state->device_state = recover_state;
>          if (ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature)) {
>              ret = -errno;
> -            error_report(
> +            error_setg(errp,
>                  "%s: Failed setting device in recover state, err: %s. 
> Resetting device",
>                           vbasedev->name, strerror(errno));
>  
> @@ -139,7 +140,7 @@ static int vfio_migration_set_state(VFIODevice *vbasedev,
>               * This can happen if the device is asynchronously reset and
>               * terminates a data transfer.
>               */
> -            error_report("%s: data_fd out of sync", vbasedev->name);
> +            error_setg(errp, "%s: data_fd out of sync", vbasedev->name);
>              close(mig_state->data_fd);
>  
>              return -EBADF;
> @@ -170,10 +171,11 @@ reset_device:
>   */
>  static int
>  vfio_migration_set_state_or_reset(VFIODevice *vbasedev,
> -                                  enum vfio_device_mig_state new_state)
> +                                  enum vfio_device_mig_state new_state,
> +                                  Error **errp)
>  {
>      return vfio_migration_set_state(vbasedev, new_state,
> -                                    VFIO_DEVICE_STATE_ERROR);
> +                                    VFIO_DEVICE_STATE_ERROR, errp);
>  }
>  
>  static int vfio_load_buffer(QEMUFile *f, VFIODevice *vbasedev,
> @@ -401,10 +403,8 @@ static int vfio_save_setup(QEMUFile *f, void *opaque, 
> Error **errp)
>          switch (migration->device_state) {
>          case VFIO_DEVICE_STATE_RUNNING:
>              ret = vfio_migration_set_state(vbasedev, 
> VFIO_DEVICE_STATE_PRE_COPY,
> -                                           VFIO_DEVICE_STATE_RUNNING);
> +                                           VFIO_DEVICE_STATE_RUNNING, errp);
>              if (ret) {
> -                error_setg(errp, "%s: Failed to set new PRE_COPY state",
> -                           vbasedev->name);
>                  return ret;
>              }
>  
> @@ -437,13 +437,20 @@ static void vfio_save_cleanup(void *opaque)
>  {
>      VFIODevice *vbasedev = opaque;
>      VFIOMigration *migration = vbasedev->migration;
> +    Error *local_err = NULL;
> +    int ret;
>  
>      /*
>       * Changing device state from STOP_COPY to STOP can take time. Do it 
> here,
>       * after migration has completed, so it won't increase downtime.
>       */
>      if (migration->device_state == VFIO_DEVICE_STATE_STOP_COPY) {
> -        vfio_migration_set_state_or_reset(vbasedev, VFIO_DEVICE_STATE_STOP);
> +        ret = vfio_migration_set_state_or_reset(vbasedev,
> +                                                VFIO_DEVICE_STATE_STOP,
> +                                                &local_err);
> +        if (ret) {
> +            error_report_err(local_err);
> +        }
>      }
>  
>      g_free(migration->data_buffer);
> @@ -549,11 +556,13 @@ static int vfio_save_complete_precopy(QEMUFile *f, void 
> *opaque)
>      VFIODevice *vbasedev = opaque;
>      ssize_t data_size;
>      int ret;
> +    Error *local_err = NULL;
>  
>      /* We reach here with device state STOP or STOP_COPY only */
>      ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_STOP_COPY,
> -                                   VFIO_DEVICE_STATE_STOP);
> +                                   VFIO_DEVICE_STATE_STOP, &local_err);
>      if (ret) {
> +        error_report_err(local_err);
>          return ret;
>      }
>  
> @@ -591,14 +600,9 @@ static void vfio_save_state(QEMUFile *f, void *opaque)
>  static int vfio_load_setup(QEMUFile *f, void *opaque, Error **errp)
>  {
>      VFIODevice *vbasedev = opaque;
> -    int ret;
>  
> -    ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RESUMING,
> -                                   vbasedev->migration->device_state);
> -    if (ret) {
> -        error_setg(errp, "%s: Failed to set RESUMING state", vbasedev->name);
> -    }
> -    return ret;
> +    return vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RESUMING,
> +                                    vbasedev->migration->device_state, errp);
>  }
>  
>  static int vfio_load_cleanup(void *opaque)
> @@ -714,20 +718,22 @@ static void vfio_vmstate_change_prepare(void *opaque, 
> bool running,
>      VFIODevice *vbasedev = opaque;
>      VFIOMigration *migration = vbasedev->migration;
>      enum vfio_device_mig_state new_state;
> +    Error *local_err = NULL;
>      int ret;
>  
>      new_state = migration->device_state == VFIO_DEVICE_STATE_PRE_COPY ?
>                      VFIO_DEVICE_STATE_PRE_COPY_P2P :
>                      VFIO_DEVICE_STATE_RUNNING_P2P;
>  
> -    ret = vfio_migration_set_state_or_reset(vbasedev, new_state);
> +    ret = vfio_migration_set_state_or_reset(vbasedev, new_state, &local_err);
>      if (ret) {
>          /*
>           * Migration should be aborted in this case, but vm_state_notify()
>           * currently does not support reporting failures.
>           */
if ret and we do not enter the condition below, we may leak the
local_err. Same below.

Eric
>          if (migrate_get_current()->to_dst_file) {
> -            qemu_file_set_error(migrate_get_current()->to_dst_file, ret);
> +            qemu_file_set_error_obj(migrate_get_current()->to_dst_file, ret,
> +                                    local_err);
>          }
>      }
>  
> @@ -740,6 +746,7 @@ static void vfio_vmstate_change(void *opaque, bool 
> running, RunState state)
>  {
>      VFIODevice *vbasedev = opaque;
>      enum vfio_device_mig_state new_state;
> +    Error *local_err = NULL;
>      int ret;
>  
>      if (running) {
> @@ -752,14 +759,15 @@ static void vfio_vmstate_change(void *opaque, bool 
> running, RunState state)
>                  VFIO_DEVICE_STATE_STOP;
>      }
>  
> -    ret = vfio_migration_set_state_or_reset(vbasedev, new_state);
> +    ret = vfio_migration_set_state_or_reset(vbasedev, new_state, &local_err);
>      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);
> +            qemu_file_set_error_obj(migrate_get_current()->to_dst_file, ret,
> +                                    local_err);
>          }
>      }
>  
> @@ -773,13 +781,16 @@ static int 
> vfio_migration_state_notifier(NotifierWithReturn *notifier,
>      VFIOMigration *migration = container_of(notifier, VFIOMigration,
>                                              migration_state);
>      VFIODevice *vbasedev = migration->vbasedev;
> +    int ret = 0;
>  
>      trace_vfio_migration_state_notifier(vbasedev->name, e->type);
>  
>      if (e->type == MIG_EVENT_PRECOPY_FAILED) {
> -        vfio_migration_set_state_or_reset(vbasedev, 
> VFIO_DEVICE_STATE_RUNNING);
> +        ret = vfio_migration_set_state_or_reset(vbasedev,
> +                                                VFIO_DEVICE_STATE_RUNNING,
> +                                                errp);
>      }
> -    return 0;
> +    return ret;
>  }
>  
>  static void vfio_migration_free(VFIODevice *vbasedev)