Re: [PATCH 2/3] tools/testing/cxl: Skip the auto region when no volatile window is active

[Richard Cheng <icheng@nvidia.com>]

On Mon, Sep 28, 2026 at 05:56:17PM +0800, Alison Schofield wrote:
> The mock auto region always uses CFMWS0. With XOR interleave arithmetic
> that window is inactive, so its HPA base is never assigned and the
> endpoint decoders are programmed at HPA 0.
> 
> No root decoder matches that range, leaving DPA allocated to endpoint
> decoders that are not part of a region.
> 
> Set up the auto region only when a volatile window is active.
> 
> Assisted-by: LLM
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> ---
>  tools/testing/cxl/test/cxl.c | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/cxl/test/cxl.c b/tools/testing/cxl/test/cxl.c
> index aa140307e0c3..9d844932f0c6 100644
> --- a/tools/testing/cxl/test/cxl.c
> +++ b/tools/testing/cxl/test/cxl.c
> @@ -423,6 +423,18 @@ struct acpi_cedt_cxims *mock_cxims[1] = {
>  	[0] = &mock_cedt.cxims0.cxims,
>  };
>  
> +static struct acpi_cedt_cfmws *mock_auto_region_cfmws(void)
> +{
> +	for (int i = cfmws_start; i <= cfmws_end; i++) {
> +		struct acpi_cedt_cfmws *window = mock_cfmws[i];
> +
> +		if (window->restrictions & ACPI_CEDT_CFMWS_RESTRICT_VOLATILE)
> +			return window;
> +	}
> +
> +	return NULL;
> +}
> +
>  struct cxl_mock_res {
>  	struct list_head list;
>  	struct range range;
> @@ -1114,6 +1126,10 @@ static enum cxld_init_type get_decoder_init_type(struct cxl_decoder *cxld,
>  	    pdev->id > 4 || cxld->id > 0)
>  		return MOCK_DECODER_INIT_DEFAULT;
>  
> +	/* XOR windows are all pmem, no window to host the RAM region */
> +	if (!mock_auto_region_cfmws())
> +		return MOCK_DECODER_INIT_DEFAULT;
> +
>  	return type2_test ? MOCK_DECODER_INIT_TYPE2_AUTO :
>  			    MOCK_DECODER_INIT_TYPE3_AUTO;
>  }
> @@ -1137,7 +1153,7 @@ static bool mock_decoder_handle_saved(struct cxl_decoder *cxld, struct cxl_test_
>  static void mock_init_hdm_type2_cxled(struct cxl_endpoint_decoder *cxled,
>  				      struct cxl_port *port)
>  {
> -	struct acpi_cedt_cfmws *window = mock_cfmws[0];
> +	struct acpi_cedt_cfmws *window = mock_auto_region_cfmws();
>  	struct cxl_decoder *cxld = &cxled->cxld;
>  	struct cxl_switch_decoder *cxlsd;
>  	struct cxl_dport *dport;
> @@ -1211,7 +1227,7 @@ static void mock_init_hdm_type3_cxled(struct cxl_endpoint_decoder *cxled,
>  				      struct platform_device *pdev,
>  				      bool hb0)
>  {
> -	struct acpi_cedt_cfmws *window = mock_cfmws[0];
> +	struct acpi_cedt_cfmws *window = mock_auto_region_cfmws();
>  	struct cxl_decoder *cxld = &cxled->cxld;
>  	struct cxl_switch_decoder *cxlsd;
>  	struct cxl_dport *dport;
> -- 
> 2.37.3
>

Hi Alison,

The caller of get_decoder_init_type() and mock_init_hdm_type2/3_cxled()
is mock_init_hdm_decoder(), would it be possible to just call
mock_auto_region_cfmws() once and pass the window into each function ?

That way we can save some redundant traversal of entries.
Do you think this idea makes sense ?

Best regards,
Richard Cheng.