[PATCH 2/2] drm/etnaviv: properly implement mmaping of imported buffers

[Daniel Vetter]

On Fri, May 25, 2018 at 03:42:54PM +0200, Lucas Stach wrote:
> The intention of the existing code was to deflect the actual work
> of mmaping a dma-buf to the exporter, as that one probably knows best
> how to handle the buffer. Unfortunately the call to drm_gem_mmap did
> more than what etnaviv needs in this case by actually setting up the
> mapping.
> 
> Move mapping setup to the shm buffer type mmap implementation so we
> only need to look up the BO and call the buffer type mmap function
> from the handler.
> 
> Fixes mmap behavior with dma-buf imported and userptr buffers.

You allow mmap on userptr buffers? That sounds really nasty ...

Also not really thrilled about dma-buf mmap forwarding either, since you
don't seem to forward the begin/end_cpu_access stuff either.
-Daniel
 
> Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
> ---
>  drivers/gpu/drm/etnaviv/etnaviv_gem.c | 30 ++++++++++++++++++++-------
>  1 file changed, 23 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> index fcc969fa0e69..f38989960d7f 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> @@ -138,6 +138,13 @@ static int etnaviv_gem_mmap_obj(struct etnaviv_gem_object *etnaviv_obj,
>  		struct vm_area_struct *vma)
>  {
>  	pgprot_t vm_page_prot;
> +	int ret;
> +
> +	ret = drm_gem_mmap_obj(&etnaviv_obj->base,
> +		drm_vma_node_size(&etnaviv_obj->base.vma_node) << PAGE_SHIFT,
> +		vma);
> +	if (ret)
> +		return ret;
>  
>  	vma->vm_flags &= ~VM_PFNMAP;
>  	vma->vm_flags |= VM_MIXEDMAP;
> @@ -167,17 +174,26 @@ static int etnaviv_gem_mmap_obj(struct etnaviv_gem_object *etnaviv_obj,
>  
>  int etnaviv_gem_mmap(struct file *filp, struct vm_area_struct *vma)
>  {
> -	struct etnaviv_gem_object *obj;
> +	struct drm_file *priv = filp->private_data;
> +	struct etnaviv_gem_object *etnaviv_obj;
> +	struct drm_gem_object *obj;
>  	int ret;
>  
> -	ret = drm_gem_mmap(filp, vma);
> -	if (ret) {
> -		DBG("mmap failed: %d", ret);
> -		return ret;
> +	obj = drm_gem_bo_vm_lookup(filp, vma);
> +	if (!obj)
> +		return -EINVAL;
> +
> +	if (!drm_vma_node_is_allowed(&obj->vma_node, priv)) {
> +		drm_gem_object_put_unlocked(obj);
> +		return -EACCES;
>  	}
>  
> -	obj = to_etnaviv_bo(vma->vm_private_data);
> -	return obj->ops->mmap(obj, vma);
> +	etnaviv_obj = to_etnaviv_bo(obj);
> +
> +	ret = etnaviv_obj->ops->mmap(etnaviv_obj, vma);
> +	drm_gem_object_put_unlocked(obj);
> +
> +	return ret;
>  }
>  
>  int etnaviv_gem_fault(struct vm_fault *vmf)
> -- 
> 2.17.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch