Re: [PATCH v3 2/2] cxl/test: Add a 2-way 16K root decoder for passthrough testing

[Richard Cheng <icheng@nvidia.com>]

On Fri, Jul 24, 2026 at 06:08:55PM +0800, Alison Schofield wrote:
> The cxl-test topologies do not provide a configuration where pass-
> through decoders compute a granularity above the 16K max encodable
> in hardware. The widest power-of-2 root decoder currently available
> is 2-way at 4K granularity, so a passthrough decoder below it
> computes at most 16K.
>

I think 2-way with 4K granularity computes 8K, not 16K.
The conclusion does hold, just the number.

 
> Add a CFMWS entry for a 2-way root decoder at 16K granularity. This
> topology supports a region configuration spanning the two multi-port
> host bridges and placing one endpoint under each bridge. The
> intermediate switch decoders are then passthrough decoders with a
> computed granularity of 32K.
> 
> This allows a CXL unit test to be added for this case.
> 
> Place the new window in the XOR topology set so the default modulo
> topology used by most cxl-test coverage is unchanged.
> 
> Assisted-by: Claude:Opus-4-8
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> ---
>  tools/testing/cxl/test/cxl.c | 48 ++++++++++++++++++++++++++++++++++--
>  1 file changed, 46 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/cxl/test/cxl.c b/tools/testing/cxl/test/cxl.c
> index ef92dd35e030..5b87a3f5673f 100644
> --- a/tools/testing/cxl/test/cxl.c
> +++ b/tools/testing/cxl/test/cxl.c
> @@ -188,10 +188,18 @@ static struct {
>  		struct acpi_cedt_cfmws cfmws;
>  		u32 target[3];
>  	} cfmws8;
> +	struct {
> +		struct acpi_cedt_cfmws cfmws;
> +		u32 target[2];
> +	} cfmws9;
>  	struct {
>  		struct acpi_cedt_cxims cxims;
>  		u64 xormap_list[2];
>  	} cxims0;
> +	struct {
> +		struct acpi_cedt_cxims cxims;
> +		u64 xormap_list[1];
> +	} cxims1;
>  } __packed mock_cedt = {
>  	.cedt = {
>  		.header = {
> @@ -371,6 +379,28 @@ static struct {
>  		},
>  		.target = { 0, 1, 2, },
>  	},
> +	/*
> +	 * A 2-way root at 16K granularity. A passthrough decoder below this
> +	 * root computes a 32K granularity (16K * 2), which exceeds the maximum
> +	 * encodable in hardware. It exercises the passthrough granularity path
> +	 * in cxl_port_setup_targets().
> +	 */
> +	.cfmws9 = {
> +		.cfmws = {
> +			.header = {
> +				.type = ACPI_CEDT_TYPE_CFMWS,
> +				.length = sizeof(mock_cedt.cfmws9),
> +			},
> +			.interleave_arithmetic = ACPI_CEDT_CFMWS_ARITHMETIC_XOR,
> +			.interleave_ways = 1,
> +			.granularity = 6,
> +			.restrictions = ACPI_CEDT_CFMWS_RESTRICT_HOSTONLYMEM |
> +					ACPI_CEDT_CFMWS_RESTRICT_PMEM,
> +			.qtg_id = FAKE_QTG_ID,
> +			.window_size = SZ_256M * 8UL,
> +		},
> +		.target = { 0, 1, },
> +	},
>  	.cxims0 = {
>  		.cxims = {
>  			.header = {
> @@ -382,6 +412,18 @@ static struct {
>  		},
>  		.xormap_list = { 0x404100, 0x808200, },
>  	},
> +	/* CXIMS for the 16K (hbig = 6) 2-way root, cfmws9 */
> +	.cxims1 = {
> +		.cxims = {
> +			.header = {
> +				.type = ACPI_CEDT_TYPE_CXIMS,
> +				.length = sizeof(mock_cedt.cxims1),
> +			},
> +			.hbig = 6,
> +			.nr_xormaps = 1,
> +		},
> +		.xormap_list = { 0x0, },
> +	},
>  };
>  
>  struct acpi_cedt_cfmws *mock_cfmws[] = {
> @@ -395,6 +437,7 @@ struct acpi_cedt_cfmws *mock_cfmws[] = {
>  	[6] = &mock_cedt.cfmws6.cfmws,
>  	[7] = &mock_cedt.cfmws7.cfmws,
>  	[8] = &mock_cedt.cfmws8.cfmws,
> +	[9] = &mock_cedt.cfmws9.cfmws,
>  };
>  
>  static int cfmws_start;
> @@ -402,10 +445,11 @@ static int cfmws_end;
>  #define CFMWS_MOD_ARRAY_START 0
>  #define CFMWS_MOD_ARRAY_END   5
>  #define CFMWS_XOR_ARRAY_START 6
> -#define CFMWS_XOR_ARRAY_END   8
> +#define CFMWS_XOR_ARRAY_END   9
>  
> -struct acpi_cedt_cxims *mock_cxims[1] = {
> +struct acpi_cedt_cxims *mock_cxims[2] = {
>  	[0] = &mock_cedt.cxims0.cxims,
> +	[1] = &mock_cedt.cxims1.cxims,
>  };
>  
>  struct cxl_mock_res {
> -- 
> 2.37.3
> 
> 

Reviewed-by: Richard Cheng <icheng@nvidia.com>

Best regards,
Richard Cheng.