Re: [PATCH v4 11/14] cxl/atl: Lock decoders that need address translation

Dave Jiang
2025-11-04T17:13:41Z

On 11/3/25 11:47 AM, Robert Richter wrote:
> There is only support to translate addresses from an endpoint to its
> CXL host bridge, but not in the opposite direction from the bridge to
> the endpoint. Thus, the endpoint address range cannot be determined
> and setup manually for a given SPA range of a region. If the endpoint
> has address translation enabled, lock it to prevent the kernel from
> reconfiguring it.
>
> Reviewed-by: Gregory Price <gourry@gourry.net>
> Signed-off-by: Robert Richter <rrichter@amd.com>
> ---
> drivers/cxl/core/atl.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/cxl/core/atl.c b/drivers/cxl/core/atl.c
> index d6aa7e6d0ac5..5c15e4d12193 100644
> --- a/drivers/cxl/core/atl.c
> +++ b/drivers/cxl/core/atl.c
> @@ -158,6 +158,16 @@ static int cxl_prm_translate_hpa_range(struct cxl_root *cxl_root, void *data)
> return -ENXIO;
> }
>
> + /*
> + * There is only support to translate from the endpoint to its
> + * parent port, but not in the opposite direction from the
> + * parent to the endpoint. Thus, the endpoint address range
> + * cannot be determined and setup manually. If the address range
> + * was translated and modified, forbid reprogramming of the
> + * decoders and lock them.
> + */
> + cxld->flags |= CXL_DECODER_F_LOCK;

Feels like this should be something the BIOS should enforce if that is the expectation? And the kernel checks and warns if that is not the case.

> +
> ctx->hpa_range = hpa_range;
> ctx->interleave_ways = ways;
> ctx->interleave_granularity = gran;