Re: [PATCH v3] cxl: docs/driver-api/conventions resolve conflicts btw CFMWS, LMH, ED

Gregory Price
2025-06-23T19:19:55Z

On Mon, Jun 23, 2025 at 05:29:02PM +0200, Fabio M. De Francesco wrote:
> Add documentation on how to resolve conflicts between CXL Fixed Memory
> Windows, Platform Memory Holes, and Endpoint Decoders.
>
> Signed-off-by: Fabio M. De Francesco <fabio.m.de.francesco@linux.intel.com>

I won't block a doc update on a suggestion so

Reviewed-by: Gregory Price <gourry@gourry.net>

> +Platform Firmware (BIOS) might reserve part of physical addresses below
> +4 GB (e.g., the Low Memory Hole that describes PCIe memory space for MMIO
> +or a requirement for the greater than 8 way interleave CXL regions starting
> +at address 0). In that case the Window Size value cannot be anymore
> +constrained to the NIW * 256 MB above-mentioned rule.

It might be nice to have a diagram that explains this visually, as it's
difficult for me to understand the implications through words alone...

which is likely why the conflict exists in the first place :]

~Gregory