Re: [PATCH v26 7/8] cxl: Avoid dax creation for accelerators

[Alison Schofield <alison.schofield@intel.com>]

On Thu, Apr 23, 2026 at 07:05:27PM +0100, alejandro.lucero-palau@amd.com wrote:
> From: Alejandro Lucero <alucerop@amd.com>
> 
> By definition a type2 cxl device will use the host managed memory for
> specific functionality, therefore it should not be available to other
> uses like DAX.
> 
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Reviewed-by: Davidlohr Bueso <daves@stgolabs.net>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Reviewed-by: Ben Cheatham <benjamin.cheatham@amd.com>
> ---
>  drivers/cxl/core/region.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 68f5a1fd1b1c..3af2aed6c6f1 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -4165,6 +4165,13 @@ static int cxl_region_probe(struct device *dev)
>  	if (rc)
>  		return rc;
>  
> +	/*
> +	 * HDM-D[B] (device-memory) regions have accelerator specific usage.
> +	 * Skip device-dax registration.
> +	 */
> +	if (cxlr->type == CXL_DECODER_DEVMEM)
> +		return 0;
> +

This decision is now made twice in cxl_region_probe(). This one above,
and another one later in the function as added by Dan's incremental:
	cxl/region: Introduce cxl_memdev_attach_region

If the intent is only to avoid dax registration, then the later one
is placed better. If the intent is different, then the commit message
and comment need updating to explain its placement.


>  	/*
>  	 * From this point on any path that changes the region's state away from
>  	 * CXL_CONFIG_COMMIT is also responsible for releasing the driver.
> -- 
> 2.34.1
> 
>