RE: [RFC PATCH 2/5] cxl/core: introduce cxl_memdev_dpa_to_hpa()

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

Shiyang Ruan wrote:
> When a memdev is assigned to a region, its Device Physical Address will be
> mapped to Host Physical Address.  Introduce this helper function to
> translate HPA from a given memdev and its DPA.
> 
> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
> ---
>  drivers/cxl/core/memdev.c | 12 ++++++++++++
>  drivers/cxl/cxlmem.h      |  1 +
>  2 files changed, 13 insertions(+)
> 
> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> index dae8802ecdb0..c304e709ef0e 100644
> --- a/drivers/cxl/core/memdev.c
> +++ b/drivers/cxl/core/memdev.c
> @@ -319,6 +319,18 @@ static int cxl_validate_poison_dpa(struct cxl_memdev *cxlmd, u64 dpa)
>  	return 0;
>  }
>  
> +phys_addr_t cxl_memdev_dpa_to_hpa(struct cxl_memdev *cxlmd, u64 dpa)
> +{
> +	struct cxl_region *cxlr = cxl_dpa_to_region(cxlmd, dpa);
> +
> +	if (cxlr)
> +		return cxlr->params.res->start + dpa;
> +	else {
> +		dev_dbg(&cxlmd->dev, "device belongs to no region.\n");
> +		return 0;
> +	}
> +}

Hmm no, I would not say memdevs are assigned to regions, *endpoint
decoders* are assigned to regions. cxl_dpa_to_region() is only an
internal helper when the endpoint decoder is unknown. Otherwise endpoint
decoders have a direct-link to their region, if mapped. See usage of
"cxled->cxld.region".