linux-kernel - Re: [RFC PATCH 0/6] Add support for shared PTEs across processes

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Message-ID: <YfFWwjzSLsZ0aV6W@kernel.org>
Date:   Wed, 26 Jan 2022 16:12:18 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     David Hildenbrand <david@...hat.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Khalid Aziz <khalid.aziz@...cle.com>,
        akpm@...ux-foundation.org, longpeng2@...wei.com, arnd@...db.de,
        dave.hansen@...ux.intel.com, surenb@...gle.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Peter Xu <peterx@...hat.com>
Subject: Re: [RFC PATCH 0/6] Add support for shared PTEs across processes

On Wed, Jan 26, 2022 at 01:38:49PM +0000, Matthew Wilcox wrote:
> On Wed, Jan 26, 2022 at 11:16:42AM +0100, David Hildenbrand wrote:
> > A while ago I talked with Peter about an extended uffd (here: WP)
> > mechanism that would work on fds instead of the process address space.
> 
> As far as I can tell, uffd is a grotesque hack that exists to work around
> the poor choice to use anonymous memory instead of file-backed memory
> in kvm.  Every time I see somebody mention it, I feel pain.

How file-backed memory would have helped for the major use-case of uffd
which is post-copy migration?

-- 
Sincerely yours,
Mike.