Re: [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM guest private memory

[Matthew Wilcox]

On Thu, Aug 18, 2022 at 08:00:41PM -0700, Hugh Dickins wrote:
> tmpfs and hugetlbfs and page cache are designed around sharing memory:
> TDX is designed around absolutely not sharing memory; and the further
> uses which Sean foresees appear not to need it as page cache either.
> 
> Except perhaps for page migration reasons.  It's somewhat incidental,  
> but of course page migration knows how to migrate page cache, so
> masquerading as page cache will give a short cut to page migration,
> when page migration becomes at all possible.

I haven't read the patch series, and I'm not taking a position one way
or the other on whether this is better implemented as a shmem addition
or a shim that asks shmem for memory.  Page migration can be done for
driver memory by using PageMovable.  I just rewrote how it works, so
the details are top of my mind at the moment if anyone wants something
explained.  Commit 68f2736a8583 is the key one to look at.