Re: [PATCH] drm/gem-dma: set VM_DONTDUMP for mmap

[Thomas Zimmermann]

Am 17.03.26 um 05:00 schrieb Chen-Yu Tsai:
> When the mmap function was converted from a file op to a GEM object
> function in commit f5ca8eb6f9bd ("drm/cma-helper: Implement mmap as GEM
> CMA object functions") some VM flags were not lifted from drm_gem_mmap():
>
>    - VM_IO
>    - VM_DONTEXPAND
>    - VM_DONTDUMP
>
> VM_DONTEXPAND was added back in commit 59f39bfa6553 ("drm/cma-helper:
> Set VM_DONTEXPAND for mmap"). VM_IO doesn't make sense since these are
> memory buffers, while "IO tells people not to look at these pages
> (accesses can have side effects)".
>
> Add back VM_DONTDUMP. This matches the behavior of most other GEM
> implementations.
>
> Signed-off-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>

I think it makes sense to not dump these buffers.

Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>

> ---
> Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
> ---
>   drivers/gpu/drm/drm_gem_dma_helper.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_dma_helper.c b/drivers/gpu/drm/drm_gem_dma_helper.c
> index ecb9746f4da8..1911bf6a6a3e 100644
> --- a/drivers/gpu/drm/drm_gem_dma_helper.c
> +++ b/drivers/gpu/drm/drm_gem_dma_helper.c
> @@ -534,7 +534,7 @@ int drm_gem_dma_mmap(struct drm_gem_dma_object *dma_obj, struct vm_area_struct *
>   	 * the whole buffer.
>   	 */
>   	vma->vm_pgoff -= drm_vma_node_start(&obj->vma_node);
> -	vm_flags_mod(vma, VM_DONTEXPAND, VM_PFNMAP);
> +	vm_flags_mod(vma, VM_DONTDUMP | VM_DONTEXPAND, VM_PFNMAP);
>   
>   	if (dma_obj->map_noncoherent) {
>   		vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);

--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)