Re: [PATCH v2 1/1] drm/xe: Prevent null pointer access in xe_migrate_copy

["Ghimiray, Himal Prasad" <himal.prasad.ghimiray@intel.com>]

On 20-09-2024 04:12, Zhanjun Dong wrote:
> Update lacks source flag to include resource is null case. This will
> prevent null pointer derefrence in xe_migrate_copy.
> 
> Signed-off-by: Zhanjun Dong <zhanjun.dong@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_bo.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> index 5f2f1ec46b57..5e8f60a8d431 100644
> --- a/drivers/gpu/drm/xe/xe_bo.c
> +++ b/drivers/gpu/drm/xe/xe_bo.c
> @@ -682,8 +682,8 @@ static int xe_bo_move(struct ttm_buffer_object *ttm_bo, bool evict,
>   	tt_has_data = ttm && (ttm_tt_is_populated(ttm) ||
>   			      (ttm->page_flags & TTM_TT_FLAG_SWAPPED));
>   
> -	move_lacks_source = handle_system_ccs ? (!bo->ccs_cleared)  :
> -						(!mem_type_is_vram(old_mem_type) && !tt_has_data);
> +	move_lacks_source = !old_mem || (handle_system_ccs ? (!bo->ccs_cleared) :
> +					 (!mem_type_is_vram(old_mem_type) && !tt_has_data));


Just for curiosity, isn't !old_mem implicitly taken care here ?
shouldn't ttm be NULL, if resource is NULL ? IIRC, this was what Thomas 
had confirmed during handle_system_ccs implementation.

Thomas/Matt,
Can you confirm here ?

BR
Himal


>   
>   	needs_clear = (ttm && ttm->page_flags & TTM_TT_FLAG_ZERO_ALLOC) ||
>   		(!ttm && ttm_bo->type == ttm_bo_type_device);