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

["Cheatham, Benjamin" <benjamin.cheatham@amd.com>]

On 4/23/2026 1:05 PM, 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 should probably go before the call to cxl_region_can_probe() to avoid
taking the cxl_rwsem. Not really a deal-breaker but would be a good optimization.

Thanks,
Ben

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