Re: [PATCH v4] cxl: docs/driver-api/conventions resolve conflicts between CFMWS, LMH, Decoders

[Gregory Price <gourry@gourry.net>]

On Wed, Aug 20, 2025 at 05:06:39PM +0200, Fabio M. De Francesco wrote:
> +
> +E.g, a real x86 platform with two CFMWS, 384 GB total memory, and LMH
> +starting at 2 GB:
> +
> +Window | CFMWS Base | CFMWS Size | HDM Decoder Base | HDM Decoder Size | Ways | Granularity
> +  0    |   0 GB     |     2 GB   |      0 GB        |       3 GB       |  12  |    256
> +  1    |   4 GB     |   380 GB   |      0 GB        |     380 GB       |  12  |    256
> +

This may be a dumb question, but... how is validation supposed to work?

Like in theory according to the above something like the following would
also be valid:

Window | CFMWS Base | CFMWS Size | HDM Decoder Base | HDM Decoder Size
  0    |   4 GB     |   380 GB   |      2 GB        |     382 GB      

(ignoring ways/granularity, i didn't adjust those).

The entirety of the CFMWS would be contained within the HDM decoder, but
with carve-outs on either end.  This would be "allowed" according to the
logic here.

This would effectively allow all HDM decoder base/size values to be valid
as long as one CFMWS is contained entirely within it.

As a result, wouldn't it then also be valid to have an HDM Decoder cover
more than one CFMWS range (two full CFMWS described by a single HDM
decoder).

That seems like it could cause issues.

~Gregory