Gregory Price wrote: > On Mon, May 12, 2025 at 06:52:31PM +0100, Matthew Wilcox wrote: > > > > > > Feel free to submit patches that deletes the existing code if you want > > > it removed from the documentation. > > > > Who sneaked that in when? > > The ACPI and EFI folks when they allowed for CXL memory to be marked > EFI_CONVENTIONAL_MEMORY - which means Linux can't actually differentiate > between DRAM and CXL during __init and brings it online in the page > allocator as SystemRAM in ZONE_NORMAL (attached to the NUMA node that > maps to the Proximity Domain in the SRAT). > > Not sure there's anything you can do about that. > > And for DAX: > > 09d09e04d2 (cxl/dax: Create dax devices for CXL RAM regions) > > Which allows for EFI_MEMORY_SP / Soft Reserved CXL regions to be brought > up as a DAX devices (which can be bound to SystemRAM via DAX kmem). > > Wasn't much sneaking going on here - DAX kmem has been around and hacked > on since 2019, and probably some years before that. Right. These interfaces have been there for a long time and this documentation is simply catching up with what is there today. I called for all of this documentation to go upstream and have no problem defending it to Linus. Appreciate all the work here Gregory! Now, is device-dax and dax_kmem the long term solution for exposing memory of this relative performance class? After LSF/MM this year I am convinced the answer is "no". Specifically I want to see a solution that meets what this astute LWN commenter recommended: https://lwn.net/Articles/1017142/ We can delete documentation and infrastructure once we have the replacement interface upstream and can start a deprecation process.
