Re: [PATCH 5/8] drm/vmwgfx: partially revert "Adapt validation code for reference-free lookups"

[Daniel Vetter <daniel.vetter@ffwll.ch>]

On Tue, Jul 23, 2024 at 02:17:47PM +0200, Christian König wrote:
> This reverts commit 64ad2abfe9a628ce79859d072704bd1ef7682044.
> 
> To me it looks like this functionality was never actually used. At least
> I can't find any protection in vmw_bo_free().

Just to double-check I've done the audit of all callers, and they all look
like they're holding a full reference indeed. The somewhat annoying case
was vmw_sw_context->cur_query_bo because it seems to not be refcounted
itself.  But that's either dev_priv->pinned_bo or
dev_priv->dummy_query_bo, both of which are refcounted, so we're good.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> 
> Signed-off-by: Christian König <christian.koenig@amd.com>
> Cc: Zack Rusin <zack.rusin@broadcom.com>
> Cc: Broadcom internal kernel review list <bcm-kernel-feedback-list@broadcom.com>
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_validation.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_validation.c b/drivers/gpu/drm/vmwgfx/vmwgfx_validation.c
> index e7625b3f71e0..e11837e484aa 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_validation.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_validation.c
> @@ -262,7 +262,8 @@ int vmw_validation_add_bo(struct vmw_validation_context *ctx,
>  				bo_node->hash.key);
>  		}
>  		val_buf = &bo_node->base;
> -		val_buf->bo = ttm_bo_get_unless_zero(&vbo->tbo);
> +		vmw_bo_reference(vbo);
> +		val_buf->bo = &vbo->tbo;
>  		if (!val_buf->bo)
>  			return -ESRCH;
>  		val_buf->num_shared = 0;
> @@ -656,7 +657,7 @@ void vmw_validation_unref_lists(struct vmw_validation_context *ctx)
>  	struct vmw_validation_res_node *val;
>  
>  	list_for_each_entry(entry, &ctx->bo_list, base.head) {
> -		ttm_bo_put(entry->base.bo);
> +		drm_gem_object_put(&entry->base.bo->base);
>  		entry->base.bo = NULL;
>  	}
>  
> -- 
> 2.34.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch