Re: [PATCH v2 02/15] cxl: Introduce callback to translate an HPA range from a port to its parent

Dave Jiang
2025-02-20T21:19:28Z

On 2/18/25 6:23 AM, Robert Richter wrote:
> To enable address translation, the endpoint's HPA range must be
> translated to each of the parent port's address ranges up to the root
> decoder. Traverse the decoder and port hierarchy from the endpoint up
> to the root port and apply platform specific translation functions to
> determine the next HPA range of the parent port where needed:
>
> if (cxl_port->to_hpa)
> hpa = cxl_port->to_hpa(cxl_decoder, hpa)
>
> The root port's HPA range is equivalent to the system's SPA range.
>
> Introduce a callback to translate an HPA range from a port to its
> parent.
>
> Signed-off-by: Robert Richter <rrichter@amd.com>
> Reviewed-by: Gregory Price <gourry@gourry.net>
> ---
> drivers/cxl/cxl.h | 11 +++++++++++
> 1 file changed, 11 insertions(+)

With such a small change, I would fold this into the patch where you are using it.

>
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index b19ba47242c6..17496784f021 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -418,6 +418,15 @@ struct cxl_switch_decoder {
> struct cxl_dport *target[];
> };
>
> +/**
> + * cxl_to_hpa_fn - type of a callback function to translate an HPA
> + * @cxld: cxl_decoder to translate from
> + * @hpa: HPA of the @cxld decoder's address range
> + *
> + * The callback translates a decoder's HPA to the next upper domain
> + * which is the address range of the decoder's parent port. The return
> + * value is the translated HPA on success or ULLONG_MAX otherwise.
> + */
> typedef u64 (*cxl_to_hpa_fn)(struct cxl_decoder *cxld, u64 hpa);
>
> /**
> @@ -581,6 +590,7 @@ struct cxl_dax_region {
> * @parent_dport: dport that points to this port in the parent
> * @decoder_ida: allocator for decoder ids
> * @reg_map: component and ras register mapping parameters
> + * @to_hpa: Callback to translate a child port's decoder address to the port's HPA address range
> * @nr_dports: number of entries in @dports
> * @hdm_end: track last allocated HDM decoder instance for allocation ordering
> * @commit_end: cursor to track highest committed decoder for commit ordering
> @@ -602,6 +612,7 @@ struct cxl_port {
> struct cxl_dport *parent_dport;
> struct ida decoder_ida;
> struct cxl_register_map reg_map;
> + cxl_to_hpa_fn to_hpa;
> int nr_dports;
> int hdm_end;
> int commit_end;