Re: [PATCH v2 0/3] cxl: Update CXL documentation for access coordinates calculation

[Dave Jiang <dave.jiang@intel.com>]

On 5/15/25 10:15 AM, Alison Schofield wrote:
> On Wed, May 14, 2025 at 05:09:20PM -0700, Dave Jiang wrote:
>> v2:
>> - Language clarifications (Gregory)
>> - Move all CDAT bits into single document. (Gregory)
>> - Define CDAT terms. (Gregory)
>>
>> Add CXL access coordinates calculation documentation including CDAT details.
> 
> I appreciate this documentation and it makes me half-smart on this
> stuff which leads to my possibly annoying questions:
> 
> Say I have a BIOS defined region. Can I look at the result of these
> calcs and see, or judge, whether BIOS set up the most efficient
> region?

Yes I think you can, since we do the calculation for all devices, not just the hot-plugged ones.

> 
> For a user created region where the topology offers some flexibility,
> can a user predict these numbers before creating a region? Can the
> user create a region, evaluate its 'perf characteristics', then destroy
> it and try another flavor?

I think so. If the QOS class mismatches, I believe you'll get a warning from CXL CLI, but you can override.

> 
> I realize this is internal docs on driver behavior and not user
> space documentation. I'm looking for info to improve my understanding
> not suggesting this info belongs in these docs.
> 
> Thanks - and, for the series:
> 
> Reviewed-by: Alison Schofield <alison.schofield@intel.com>
> 
>>
>>
>> Dave Jiang (3):
>>   cxl: docs/platform/cdat reference documentation
>>   cxl: docs/platform/acpi/srat Add generic target documentation
>>   cxl: doc/linux/access-coordinates Update access coordinates
>>     calculation methods
>>
>>  Documentation/driver-api/cxl/index.rst        |   1 +
>>  .../cxl/linux/access-coordinates.rst          |  86 +++++++++++++
>>  .../driver-api/cxl/platform/acpi/srat.rst     |  27 ++++
>>  .../driver-api/cxl/platform/cdat.rst          | 118 ++++++++++++++++++
>>  4 files changed, 232 insertions(+)
>>  create mode 100644 Documentation/driver-api/cxl/platform/cdat.rst
>>
>>
>> base-commit: 7855bc1362518673103bd9357827572207e6f6d9
>> -- 
>> 2.49.0
>>