Re: [PATCH 2/2] drm/xe: Copy cpu_caching when importing DMA-BUF.

[Matthew Brost <matthew.brost@intel.com>]

On Thu, Mar 20, 2025 at 10:15:19PM +0100, Maarten Lankhorst wrote:
> When testing xe with P2PDMA DMA-BUF import,
> VM_BIND was failing because cpu_caching was not set.
> 
> Set cpu_caching if available from another xe driver,
> to allow uncached VM_BIND on imported DMA-BUF.
> 
> Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> ---
>  drivers/gpu/drm/xe/xe_dma_buf.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_dma_buf.c b/drivers/gpu/drm/xe/xe_dma_buf.c
> index c5b95470fa324..9b1813e65e0a4 100644
> --- a/drivers/gpu/drm/xe/xe_dma_buf.c
> +++ b/drivers/gpu/drm/xe/xe_dma_buf.c
> @@ -266,12 +266,12 @@ struct drm_gem_object *xe_gem_prime_import(struct drm_device *dev,
>  	const struct dma_buf_attach_ops *attach_ops;
>  	struct dma_buf_attachment *attach;
>  	struct drm_gem_object *obj;
> -	struct xe_bo *bo;
> +	struct xe_bo *bo, *foreign_bo = NULL;
>  
> -	if (dma_buf->ops == &xe_dmabuf_ops) {
> +	if (dma_buf->ops == &xe_dmabuf_ops &&
> +	    !XE_TEST_ONLY(test && test->force_different_devices)) {
>  		obj = dma_buf->priv;
> -		if (obj->dev == dev &&
> -		    !XE_TEST_ONLY(test && test->force_different_devices)) {
> +		if (obj->dev == dev) {
>  			/*
>  			 * Importing dmabuf exported from out own gem increases
>  			 * refcount on gem itself instead of f_count of dmabuf.
> @@ -279,6 +279,8 @@ struct drm_gem_object *xe_gem_prime_import(struct drm_device *dev,
>  			drm_gem_object_get(obj);
>  			return obj;
>  		}
> +
> +		foreign_bo = gem_to_xe_bo(obj);
>  	}
>  
>  	/*
> @@ -310,6 +312,9 @@ struct drm_gem_object *xe_gem_prime_import(struct drm_device *dev,
>  
>  	get_dma_buf(dma_buf);
>  	obj->import_attach = attach;
> +	if (foreign_bo)
> +		bo->cpu_caching = foreign_bo->cpu_caching;
> +
>  	return obj;
>  
>  out_err:
> -- 
> 2.45.2
>