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

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Date:   Tue, 25 Jan 2022 14:18:57 +0100
From:   David Hildenbrand <david@...hat.com>
To:     William Kucharski <kucharsk@...il.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Khalid Aziz <khalid.aziz@...cle.com>, akpm@...ux-foundation.org,
        willy@...radead.org, longpeng2@...wei.com, arnd@...db.de,
        dave.hansen@...ux.intel.com, rppt@...nel.org, surenb@...gle.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC PATCH 0/6] Add support for shared PTEs across processes

On 25.01.22 13:09, William Kucharski wrote:
> I would think this should be the case; certainly it seems to be a more effective approach than having to manually enable sharing via the API in every case or via changes to ld.so.
> 
> If anything it might be useful to have an API for shutting it off, though there are already multiple areas where the system shares resources in ways that cannot be shut off by user action.
> 

I don't have time to look into details right now, but I see various
possible hard-to-handle issues with sharing anon pages via this
mechanism between processes. If we could restrict it to MAP_SHARED and
have some magic toggle to opt in, that would be great. Features like
uffd that we might soon see on some MAP_SHARED pages will require to not
share page tables automatically I assume.

-- 
Thanks,

David / dhildenb