Re: [PATCH RFC 4/7] PCI/P2PDMA: Prefer providers with better HMAT performance

[Logan Gunthorpe]

On 2026-08-16 06:38, Leon Romanovsky wrote:
>> This feels backwards to me. If ACPI is kind enough to include
>> information on P2PDMA support then I feel like we should use it
>> exclusively. Not prioritize the old janky whitelists.
> 
> Right now, there is no ACPI support, and I chose to prioritize
> existing systems that already have some form of support over an ACPI
> solution that does not yet exist.
But don't we know whether ACPI is advertising support now? Certainly if
ACPI indicates support we should use it above all other considerations
today. Otherwise fall back on the white lists. And that should always
work. Even on my old hardware because the ACPI on that machine doesn't
advertise support, so it should fall back on the whitelist. I see no
need to ever check the whitelist before checking ACPI.

Logan