linux-kernel - Re: [PATCH v2 1/4] mm: Introduce vm_uffd

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Message-ID: <aGWmZKwcpLMfAN2O@x1.local>
Date: Wed, 2 Jul 2025 17:36:36 -0400
From: Peter Xu <peterx@...hat.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Nikita Kalyazin <kalyazin@...zon.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Suren Baghdasaryan <surenb@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Vlastimil Babka <vbabka@...e.cz>,
	Muchun Song <muchun.song@...ux.dev>,
	Mike Rapoport <rppt@...nel.org>, Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	James Houghton <jthoughton@...gle.com>,
	Michal Hocko <mhocko@...e.com>,
	David Hildenbrand <david@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Oscar Salvador <osalvador@...e.de>,
	Axel Rasmussen <axelrasmussen@...gle.com>,
	Ujwal Kundur <ujwal.kundur@...il.com>
Subject: Re: [PATCH v2 1/4] mm: Introduce vm_uffd_ops API

On Wed, Jul 02, 2025 at 05:24:02PM -0400, Liam R. Howlett wrote:
> That's because the entry point is from a function pointer, so [3] won't
> help at all.
> 
> It is recreating the situation that existed for the vma through the
> vm_ops in mmap, but for uffd.  And at a lower level (page tables).  I do not
> want to relive that experience.
> 
> We are not doing this.  It is for the benefit of everyone that we are
> not doing this.

Is the vma issue about "allowing vma->vm_flags to be modified anywhere"
issue?  Or is there a pointer to the issue being discussed if not?

> 
> We need to find another way.

Could you suggest something?  The minimum goal is to allow guest-memfd
support minor faults.

Thanks,

-- 
Peter Xu