Re: [PATCH 2/6] drm/msm/gem: Mmap imported dma-bufs via the exporter

["Christian König" <christian.koenig@amd.com>]

On 9/26/26 20:30, Rob Clark wrote:
> This was always the way it was supposed to work, and when we drop the
> page array for imported dma-bufs our fault handling path will no longer
> work.
> 
> Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>

Nice to see that finally happening.

Reviewed-by: Christian König <christian.koenig@amd.com> for this patch here, Acked-by: Christian König <christian.koenig@amd.com> for the rest of the series.

Regards,
Christian.

> ---
>  drivers/gpu/drm/msm/msm_gem.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
> index e8390ebd5dd5..c90336b3b231 100644
> --- a/drivers/gpu/drm/msm/msm_gem.c
> +++ b/drivers/gpu/drm/msm/msm_gem.c
> @@ -23,6 +23,8 @@
>  #include "msm_gpu.h"
>  #include "msm_kms.h"
>  
> +MODULE_IMPORT_NS("DMA_BUF");
> +
>  static void update_device_mem(struct msm_drm_private *priv, ssize_t size)
>  {
>  	uint64_t total_mem = atomic64_add_return(size, &priv->total_mem);
> @@ -338,6 +340,9 @@ static vm_fault_t msm_gem_fault(struct vm_fault *vmf)
>  	int err;
>  	vm_fault_t ret;
>  
> +	if (drm_WARN_ON_ONCE(obj->dev, drm_gem_is_imported(obj)))
> +		return VM_FAULT_SIGBUS;
> +
>  	/*
>  	 * vm_ops.open/drm_gem_mmap_obj and close get and put
>  	 * a reference on obj. So, we dont need to hold one here.
> @@ -1126,6 +1131,25 @@ static int msm_gem_object_mmap(struct drm_gem_object *obj, struct vm_area_struct
>  {
>  	struct msm_gem_object *msm_obj = to_msm_bo(obj);
>  
> +	if (drm_gem_is_imported(obj)) {
> +		int ret;
> +
> +		/* Reset both vm_ops and vm_private_data, so we don't end up with
> +		 * vm_ops pointing to our implementation if the dma-buf backend
> +		 * doesn't set those fields.
> +		 */
> +		vma->vm_private_data = NULL;
> +		vma->vm_ops = NULL;
> +
> +		ret = dma_buf_mmap(obj->dma_buf, vma, 0);
> +
> +		/* Drop the reference drm_gem_mmap_obj() acquired.*/
> +		if (!ret)
> +			drm_gem_object_put(obj);
> +
> +		return ret;
> +	}
> +
>  	vm_flags_set(vma, VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
>  	vma->vm_page_prot = msm_gem_pgprot(msm_obj, vma_get_page_prot(vma));
>