Re: [PATCH v4 17/25] vfio: Add Error** argument to vfio_devices_dma_logging_start()

[Eric Auger]

Hi Cédric,

On 3/6/24 14:34, Cédric Le Goater wrote:
> This allows to update the Error argument of the VFIO log_global_start()
> handler. Errors detected when device level logging is started will be
> propagated up to qemu_savevm_state_setup() when the ram save_setup()
> handler is executed.
> 
> The vfio_set_migration_error() call becomes redundant. Remove it.
you may precise it becomes redundant in vfio_listener_log_global_start()
because it is kept in vfio_listener_log_global_stop
> 
> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Signed-off-by: Cédric Le Goater <clg@redhat.com>
> ---
> 
>  Changes in v4:
> 
>  - Dropped log_global_stop() and log_global_sync() changes
>    
>  Changes in v3:
> 
>  - Use error_setg_errno() in vfio_devices_dma_logging_start() 
>  - ERRP_GUARD() because of error_prepend use in
>    vfio_listener_log_global_start()
>    
>  hw/vfio/common.c | 25 ++++++++++++++-----------
>  1 file changed, 14 insertions(+), 11 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 
> 5598a508399a6c0b3a20ba17311cbe83d84250c5..d6790557da2f2890398fa03dbbef18129cd2c1bb
>  100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -1036,7 +1036,8 @@ static void 
> vfio_device_feature_dma_logging_start_destroy(
>      g_free(feature);
>  }
>  
> -static int vfio_devices_dma_logging_start(VFIOContainerBase *bcontainer)
> +static int vfio_devices_dma_logging_start(VFIOContainerBase *bcontainer,
> +                                          Error **errp)
>  {
>      struct vfio_device_feature *feature;
>      VFIODirtyRanges ranges;
> @@ -1058,8 +1059,8 @@ static int 
> vfio_devices_dma_logging_start(VFIOContainerBase *bcontainer)
>          ret = ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature);
>          if (ret) {
>              ret = -errno;
there is another case of error if !feature. Don't we want t o set errp
in that case as well?
I think in general we should try to make the return value and the errp
consistent because the caller may try to exploit the errp in case or
negative returned value.
> -            error_report("%s: Failed to start DMA logging, err %d (%s)",
> -                         vbasedev->name, ret, strerror(errno));
> +            error_setg_errno(errp, errno, "%s: Failed to start DMA logging",
> +                             vbasedev->name);
>              goto out;
>          }
>          vbasedev->dirty_tracking = true;
> @@ -1078,20 +1079,19 @@ out:
>  static bool vfio_listener_log_global_start(MemoryListener *listener,
>                                             Error **errp)
>  {
> +    ERRP_GUARD(); /* error_prepend use */
>      VFIOContainerBase *bcontainer = container_of(listener, VFIOContainerBase,
>                                                   listener);
>      int ret;
>  
>      if (vfio_devices_all_device_dirty_tracking(bcontainer)) {
> -        ret = vfio_devices_dma_logging_start(bcontainer);
> +        ret = vfio_devices_dma_logging_start(bcontainer, errp);
>      } else {
> -        ret = vfio_container_set_dirty_page_tracking(bcontainer, true, NULL);
> +        ret = vfio_container_set_dirty_page_tracking(bcontainer, true, errp);
>      }
>  
>      if (ret) {
> -        error_report("vfio: Could not start dirty page tracking, err: %d 
> (%s)",
> -                     ret, strerror(-ret));
> -        vfio_set_migration_error(ret);
> +        error_prepend(errp, "vfio: Could not start dirty page tracking - ");
>      }
>      return !ret;
>  }
> @@ -1100,17 +1100,20 @@ static void 
> vfio_listener_log_global_stop(MemoryListener *listener)
>  {
>      VFIOContainerBase *bcontainer = container_of(listener, VFIOContainerBase,
>                                                   listener);
> +    Error *local_err = NULL;
>      int ret = 0;
>  
>      if (vfio_devices_all_device_dirty_tracking(bcontainer)) {
>          vfio_devices_dma_logging_stop(bcontainer);
>      } else {
> -        ret = vfio_container_set_dirty_page_tracking(bcontainer, false, 
> NULL);
> +        ret = vfio_container_set_dirty_page_tracking(bcontainer, false,
> +                                                     &local_err);
>      }
>  
>      if (ret) {
> -        error_report("vfio: Could not stop dirty page tracking, err: %d 
> (%s)",
> -                     ret, strerror(-ret));
> +        error_prepend(&local_err,
> +                      "vfio: Could not stop dirty page tracking - ");
> +        error_report_err(local_err);
>          vfio_set_migration_error(ret);
>      }
>  }
Eric