linux-kernel - Re: [PATCH v4 0/4] mm/userfaultfd: modulize memory types

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Message-ID: <52e064b1-819a-47b3-9f4e-7ab0890841e7@kernel.org>
Date: Tue, 4 Nov 2025 13:23:49 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Mike Rapoport <rppt@...nel.org>
Cc: Peter Xu <peterx@...hat.com>, Lorenzo Stoakes
 <lorenzo.stoakes@...cle.com>, "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 Muchun Song <muchun.song@...ux.dev>, Nikita Kalyazin <kalyazin@...zon.com>,
 Vlastimil Babka <vbabka@...e.cz>, Axel Rasmussen <axelrasmussen@...gle.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 James Houghton <jthoughton@...gle.com>, Hugh Dickins <hughd@...gle.com>,
 Michal Hocko <mhocko@...e.com>, Ujwal Kundur <ujwal.kundur@...il.com>,
 Oscar Salvador <osalvador@...e.de>, Suren Baghdasaryan <surenb@...gle.com>,
 Andrea Arcangeli <aarcange@...hat.com>, conduct@...nel.org
Subject: Re: [PATCH v4 0/4] mm/userfaultfd: modulize memory types

On 04.11.25 08:21, Mike Rapoport wrote:
> On Mon, Nov 03, 2025 at 10:27:05PM +0100, David Hildenbrand (Red Hat) wrote:
>>
>> And maybe that's the main problem here: Liam talks about general uffd
>> cleanups while you are focused on supporting guest_memfd minor mode "as
>> simple as possible" (as you write below).
> 
> Hijacking for the technical part for a moment ;-)

What?! That's crazy :P

> 
> It seems that "as simple as possible" can even avoid data members in struct
> vm_uffd_ops, e.g something along these lines:

Right, that's certainly even more "minimal".

In the end I agree with previous assessment that the original series is 
not completely a "modulize memory types".

If we want to make it easier for guest_memfd to support 
MFILL_ATOMIC_CONTINUE, then maybe we should focus on that, and only 
that, for the time being to make progress.

-- 
Cheers

David