Re: [RFC PATCH 00/12] dax: Add DAX to guest memfd support for KVM

[Gregory Price <gourry@gourry.net>]

On Wed, Apr 29, 2026 at 08:21:00AM -0500, Ira Weiny wrote:
> Gregory Price wrote:

I think we're largely in agreement here, so trimming a bunch of this.

> > 
> > The question is ultimately how much flexibility you need to shuffle this
> > capacity from one guest to another.
> 
> Yep.  And how much control one needs over which exact CXL/DAX devices the
> memory comes from.  As you know from our community calls that is one thing
> I'm not sure the private node idea is great at.  But it could be that is
> not really required.  Or is best handled as a carve out.
> 

If you can do Device<->Node mappings, then this is trivial.

If you need more specific handling, then private nodes are not the way.

The intent of private nodes is to make mmap()/malloc() etc functional in
a heterogenous memory world, which is explicitly different than "give me
a specific chunk of physical capacity".

Which, tl;dr:  "There's a real argument for just handing guest_memfd a
chunk of unmapped memory and making it deal with the problem".

(shared gmem is... odd... given the original intent not do this :P)

~Gregory