Re: [PATCH v7 11/11] cxl/atl: Lock decoders that need address translation

[Dave Jiang <dave.jiang@intel.com>]

On 11/14/25 2:39 PM, Robert Richter wrote:
> The current kernel implementation does not support endpoint setup with
> Normalized Addressing. It only translates an endpoint's DPA to the SPA
> range of the host bridge. Therefore, the endpoint address range cannot
> be determined, making a non-auto setup impossible. If a decoder
> requires address translation, reprogramming should be disabled and the
> decoder locked.
> 
> The BIOS, however, provides all the necessary address translation
> data, which the kernel can use to reconfigure endpoint decoders with
> normalized addresses. Locking the decoders in the BIOS would prevent a
> capable kernel (or other operating systems) from shutting down
> auto-generated regions and managing resources dynamically.
> 
> Reviewed-by: Gregory Price <gourry@gourry.net>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> Tested-by: Gregory Price <gourry@gourry.net>
> Signed-off-by: Robert Richter <rrichter@amd.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>> ---
>  drivers/cxl/core/atl.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/cxl/core/atl.c b/drivers/cxl/core/atl.c
> index 3b02999d3c59..0590890bd093 100644
> --- a/drivers/cxl/core/atl.c
> +++ b/drivers/cxl/core/atl.c
> @@ -161,6 +161,24 @@ static int cxl_prm_translate_hpa_range(struct cxl_root *cxl_root, void *data)
>  		return -ENXIO;
>  	}
>  
> +	/*
> +	 * The current kernel implementation does not support endpoint
> +	 * setup with Normalized Addressing. It only translates an
> +	 * endpoint's DPA to the SPA range of the host bridge.
> +	 * Therefore, the endpoint address range cannot be determined,
> +	 * making a non-auto setup impossible. If a decoder requires
> +	 * address translation, reprogramming should be disabled and
> +	 * the decoder locked.
> +	 *
> +	 * The BIOS, however, provides all the necessary address
> +	 * translation data, which the kernel can use to reconfigure
> +	 * endpoint decoders with normalized addresses. Locking the
> +	 * decoders in the BIOS would prevent a capable kernel (or
> +	 * other operating systems) from shutting down auto-generated
> +	 * regions and managing resources dynamically.
> +	 */
> +	cxld->flags |= CXL_DECODER_F_LOCK;
> +
>  	ctx->hpa_range = hpa_range;
>  	ctx->interleave_ways = ways;
>  	ctx->interleave_granularity = gran;