Re: [PATCH 1/2] x86/numa: Introduce numa_fill_memblks()

[Alison Schofield]

On Thu, May 18, 2023 at 05:08:16PM -0700, Dave Hansen wrote:
> On 5/18/23 17:04, alison.schofield@xxxxxxxxx wrote:
> > The initial use case is the ACPI driver that needs to extend
> > SRAT defined proximity domains to an entire CXL CFMWS Window[1].
> 
> Dumb question time: Why didn't the SRAT just cover this sucker in the
> first place?  Are we fixing up a BIOS bug or is there a legitimate
> reason that the SRAT didn't cover it up front?
> 
>

There is no requirement that the BIOS describe (in the SRAT) all the
HPA assigned to a CFMWS Window. The HPA range may not actually map to
any memory at boot time. It can be persistent capacity or may be there
to enable hot-plug. IIUC BIOS can pick and choose and define volatile
regions wherever it pleases.

So, no we're not fixing up a BIOS bug, nor doing a BIOS sanity check.