Re: [PATCH] drm/ttm: update bulk move object of ghost BO

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 01.09.22 um 11:29 schrieb ZhenGuo Yin:
> [Why]
> Ghost BO is released with non-empty bulk move object. There is a
> warning trace:
> WARNING: CPU: 19 PID: 1582 at ttm/ttm_bo.c:366 ttm_bo_release+0x2e1/0x2f0 [amdttm]
> Call Trace:
>    amddma_resv_reserve_fences+0x10d/0x1f0 [amdkcl]
>    amdttm_bo_put+0x28/0x30 [amdttm]
>    amdttm_bo_move_accel_cleanup+0x126/0x200 [amdttm]
>    amdgpu_bo_move+0x1a8/0x770 [amdgpu]
>    ttm_bo_handle_move_mem+0xb0/0x140 [amdttm]
>    amdttm_bo_validate+0xbf/0x100 [amdttm]
>
> [How]
> The resource of ghost BO should be moved to LRU directly, instead of
> using bulk move. The bulk move object of ghost BO should set to NULL
> before function ttm_bo_move_to_lru_tail_unlocked.
>
> Fixed:·5b951e487fd6bf5f·("drm/ttm:·fix·bulk·move·handling·v2")
> Signed-off-by: ZhenGuo Yin <zhenguo.yin@amd.com>

Good catch, but the fix is not 100% correct. Please rather just NULL the 
member while initializing the BO structure.

E.g. something like this:

  ....
  fbo->base.pin_count = 0;
+fbo->base.bulk_move= NULL;
  if (bo->type != ttm_bo_type_sg)
  ....

Thanks,
Christian.

> ---
>   drivers/gpu/drm/ttm/ttm_bo_util.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
> index 1cbfb00c1d65..a90bbbd91910 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
> @@ -238,6 +238,7 @@ static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
>   
>   	if (fbo->base.resource) {
>   		ttm_resource_set_bo(fbo->base.resource, &fbo->base);
> +		ttm_bo_set_bulk_move(&fbo->base, NULL);
>   		bo->resource = NULL;
>   	}
>