Re: [RFC PATCH 1/5] cxl/region: Only allow CXL capable targets

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Thu, 17 Jun 2021 17:51:56 -0700
Ben Widawsky <ben.widawsky@intel.com> wrote:

> A cxl_memdev exists for all CXL endpoints that support the CXL.io
> protocol. If that device cannot participate in CXL.mem protocol, then it
> cannot be part of a region's interleave set.
> 
> The ABI allows setting a target which is currently not CXL.mem capable
> and only will fail when the binding to the region driver occurs. This is
> in line with the other configuration parameters which are only strictly
> validated when the driver gets bound to the region.
> 
> Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> ---
>  drivers/cxl/mem.h    |  5 +++++
>  drivers/cxl/region.c | 12 +++++++++++-
>  2 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/mem.h b/drivers/cxl/mem.h
> index ff1f9c57e089..3d51bf6c090f 100644
> --- a/drivers/cxl/mem.h
> +++ b/drivers/cxl/mem.h
> @@ -84,4 +84,9 @@ struct cxl_mem {
>  	struct range ram_range;
>  };
>  
> +static inline bool is_cxl_capable(struct cxl_memdev *cxlmd)

is_cxl_mem_capable()?

Can be cxl capable in many other senses!

> +{
> +	return false;
> +}
> +
>  #endif /* __CXL_MEM_H__ */
> diff --git a/drivers/cxl/region.c b/drivers/cxl/region.c
> index 2e73ece001ec..837f4314ffcc 100644
> --- a/drivers/cxl/region.c
> +++ b/drivers/cxl/region.c
> @@ -176,6 +176,10 @@ static size_t set_targetN(struct cxl_region *region, const char *buf, int n, siz
>  		return -ENOENT;
>  
>  	cxlmd = to_cxl_memdev(memdev_dev);
> +	if (!is_cxl_capable(cxlmd))
> +		dev_dbg(&region->dev,
> +			"Setting a target which doesn't support CXL.mem");
> +
>  	get_device(&cxlmd->dev);
>  	region->targets[n] = cxlmd;
>  
> @@ -432,11 +436,17 @@ static int bind_region(struct cxl_region *region)
>  		return -ENXIO;
>  	}
>  
> -	for (i = 0; i < region->eniw; i++)
> +	for (i = 0; i < region->eniw; i++) {
>  		if (!region->targets[i]) {
>  			trace_cxl_region_bind(region, "Missing memory device target");
>  			return -ENXIO;
>  		}
> +		if (!is_cxl_capable(region->targets[i])) {
> +			trace_cxl_region_bind(region,
> +					      "Target isn't CXL.mem capable");
> +			return -ENODEV;
> +		}
> +	}
>  
>  	rc = allocate_region_addr(region);
>  	if (rc)