Re: [PATCH 4/5] cxl: Set type of region to that of the first endpoint

[Dan Williams <dan.j.williams@intel.com>]

Huang Ying wrote:
> Current kernel hard-codes the type of region to type 3 expander now,
> because this is the only supported device type.  As a preparation to
> support type 2 accelerators, the patch sets the type of region to that
> of the first endpoint.  Then, the patch checks whether the type of
> region is same as the type of other endpoints of the region.  Because
> what we really need is to make sure the type of all endpoints of a
> region is same.  And, the patch lets expander/accelerator device
> drivers specify the target type of endpoint devices via struct
> cxl_dev_state.
> 
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> Reviewed-by: Gregory Price <gourry@gourry.net>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Davidlohr Bueso <dave@stgolabs.net>
> Cc: Jonathan Cameron <jonathan.cameron@huawei.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Alison Schofield <alison.schofield@intel.com>
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Cc: Alejandro Lucero <alucerop@amd.com>
> Cc: Ben Cheatham <benjamin.cheatham@amd.com>
> ---
>  drivers/cxl/acpi.c        |  1 -
>  drivers/cxl/core/hdm.c    | 28 +++++++++++++---------------
>  drivers/cxl/core/port.c   |  2 ++
>  drivers/cxl/core/region.c | 13 +++++++------
>  drivers/cxl/cxl.h         |  1 +
>  5 files changed, 23 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index 21486e471305..29c2a44b122c 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -382,7 +382,6 @@ static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
>  
>  	cxld = &cxlrd->cxlsd.cxld;
>  	cxld->flags = cfmws_to_decoder_flags(cfmws->restrictions);
> -	cxld->target_type = CXL_DECODER_EXPANDER;
>  	cxld->hpa_range = (struct range) {
>  		.start = cfmws->base_hpa,
>  		.end = cfmws->base_hpa + cfmws->window_size - 1,
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 478fb6691759..c9accf8be71f 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -841,18 +841,25 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
>  		.end = base + size - 1,
>  	};
>  
> +	if (cxled) {
> +		struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> +		struct cxl_dev_state *cxlds = cxlmd->cxlds;
> +
> +		if (cxlds->type == CXL_DEVTYPE_CLASSMEM)
> +			cxld->target_type = CXL_DECODER_EXPANDER;
> +		else
> +			cxld->target_type = CXL_DECODER_ACCEL;

This looks broken there is no way to know the target type of the decoder
from the cxl_dev_state. An "accelerator" can have HDM and an "expander"
can have HDM-DB.

> +	}
> +
>  	/* decoders are enabled if committed */
>  	if (committed) {
>  		cxld->flags |= CXL_DECODER_F_ENABLE;
>  		if (ctrl & CXL_HDM_DECODER0_CTRL_LOCK)
>  			cxld->flags |= CXL_DECODER_F_LOCK;
> -		if (FIELD_GET(CXL_HDM_DECODER0_CTRL_HOSTONLY, ctrl)) {
> -			cxld->target_type = CXL_DECODER_EXPANDER;
> +		if (FIELD_GET(CXL_HDM_DECODER0_CTRL_HOSTONLY, ctrl))
>  			cxld->coherence = CXL_DECODER_HOSTONLYCOH;
> -		} else {
> -			cxld->target_type = CXL_DECODER_ACCEL;
> +		else
>  			cxld->coherence = CXL_DECODER_DEVCOH;
> -		}
>  
>  		guard(rwsem_write)(&cxl_region_rwsem);
>  		if (cxld->id != cxl_num_decoders_committed(port)) {
> @@ -874,21 +881,12 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
>  			struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
>  			struct cxl_dev_state *cxlds = cxlmd->cxlds;
>  
> -			/*
> -			 * Default by devtype until a device arrives that needs
> -			 * more precision.
> -			 */
> -			if (cxlds->type == CXL_DEVTYPE_CLASSMEM)
> -				cxld->target_type = CXL_DECODER_EXPANDER;
> -			else
> -				cxld->target_type = CXL_DECODER_ACCEL;
>  			if (cxlds->coherence == CXL_DEVCOH_HOSTONLY)
>  				cxld->coherence = CXL_DECODER_HOSTONLYCOH;
>  			else
>  				cxld->coherence = CXL_DECODER_DEVCOH;
>  		} else {
> -			/* To be overridden by region type/coherence at commit time */
> -			cxld->target_type = CXL_DECODER_EXPANDER;
> +			/* To be overridden by region coherence at commit time */
>  			cxld->coherence = CXL_DECODER_HOSTONLYCOH;
>  		}
>  
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 9ebbffcea26a..d1bc6aed6509 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -139,6 +139,8 @@ static ssize_t target_type_show(struct device *dev,
>  		return sysfs_emit(buf, "accelerator\n");
>  	case CXL_DECODER_EXPANDER:
>  		return sysfs_emit(buf, "expander\n");
> +	default:
> +		break;
>  	}
>  	return -ENXIO;
>  }
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 21b877d8582f..d709738ada61 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1926,7 +1926,10 @@ static int cxl_region_attach(struct cxl_region *cxlr,
>  		return -ENXIO;
>  	}
>  
> -	if (cxled->cxld.target_type != cxlr->type) {
> +	/* Set the type of region to that of the first endpoint */
> +	if (cxlr->type == CXL_DECODER_INVALID) {
> +		cxlr->type = cxled->cxld.target_type;
> +	} else if (cxled->cxld.target_type != cxlr->type) {

No, the type of the region is determined by the caller and should be
gated by the region capability. For type-2 region creation I doubt
userspace is going to be creating those vs the accelerator so this all
seems backwards to me.