Re: [PATCH v4 08/14] cxl: Introduce callback for HPA address ranges translation

Dave Jiang
2025-11-03T23:09:11Z

On 11/3/25 11:47 AM, Robert Richter wrote:
> Introduce a callback to translate an endpoint's HPA range to the
> address range of the root port which is the System Physical Address
> (SPA) range used by a region. The callback can be set if a platform
> needs to handle address translation.
>
> The callback is attached to the root port. An endpoint's root port can
> easily be determined in the PCI hierarchy without any CXL specific
> knowledge. This allows the early use of address translation for CXL
> enumeration. Address translation is esp. needed for the detection of
> the root decoders. Thus, the callback is embedded in struct
> cxl_root_ops instead of struct cxl_rd_ops.
>
> Signed-off-by: Robert Richter <rrichter@amd.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>> ---
> drivers/cxl/core/region.c | 19 +++++++++++++++++++
> drivers/cxl/cxl.h | 1 +
> 2 files changed, 20 insertions(+)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 2dd9e9be4889..379a67cc8e31 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -3364,6 +3364,15 @@ static int match_root_decoder(struct device *dev, const void *data)
> return range_contains(r1, r2);
> }
>
> +static int translate_hpa_range(struct cxl_root *cxl_root,
> + struct cxl_region_context *ctx)
> +{
> + if (!cxl_root->ops.translate_hpa_range)
> + return 0;
> +
> + return cxl_root->ops.translate_hpa_range(cxl_root, ctx);
> +}
> +
> static struct cxl_root_decoder *
> get_cxl_root_decoder(struct cxl_endpoint_decoder *cxled,
> struct cxl_region_context *ctx)
> @@ -3371,6 +3380,16 @@ get_cxl_root_decoder(struct cxl_endpoint_decoder *cxled,
> struct cxl_port *port = cxled_to_port(cxled);
> struct cxl_root *cxl_root __free(put_cxl_root) = find_cxl_root(port);
> struct device *cxlrd_dev;
> + int rc;
> +
> + rc = translate_hpa_range(cxl_root, ctx);
> + if (rc) {
> + dev_err(port->uport_dev,
> + "%s:%s Failed to translate address range %#llx:%#llx\n",
> + dev_name(&ctx->cxlmd->dev), dev_name(&cxled->cxld.dev),
> + ctx->hpa_range.start, ctx->hpa_range.end);
> + return ERR_PTR(rc);
> + }
>
> cxlrd_dev = device_find_child(&cxl_root->port.dev, &ctx->hpa_range,
> match_root_decoder);
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 9a381c827416..94b9fcc07469 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -644,6 +644,7 @@ struct cxl_root_ops {
> int (*qos_class)(struct cxl_root *cxl_root,
> struct access_coordinate *coord, int entries,
> int *qos_class);
> + int (*translate_hpa_range)(struct cxl_root *cxl_root, void *data);
> };
>
> /**