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To:     Emil Velikov <emil.l.velikov@gmail.com>,
        Chris Wilson <chris@chris-wilson.co.uk>
Cc:     Will Drewry <wad@chromium.org>, Kees Cook <keescook@chromium.org>,
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        Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
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        ML dri-devel <dri-devel@lists.freedesktop.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        "# 3.13+" <stable@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
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From:   =?UTF-8?Q?Michel_D=c3=a4nzer?= <michel@daenzer.net>
Subject: Re: [PATCH v3] kcmp: Support selection of SYS_kcmp without
 CHECKPOINT_RESTORE
Message-ID: <3a2316b6-27a9-d56a-b488-ac15a402a0d2@daenzer.net>
Date:   Fri, 12 Feb 2021 15:01:16 +0100
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On 2021-02-12 1:57 p.m., Emil Velikov wrote:
> On Fri, 5 Feb 2021 at 22:01, Chris Wilson <chris@chris-wilson.co.uk> wrote:
>>
>> Userspace has discovered the functionality offered by SYS_kcmp and has
>> started to depend upon it. In particular, Mesa uses SYS_kcmp for
>> os_same_file_description() in order to identify when two fd (e.g. device
>> or dmabuf)
> 
> As you rightfully point out, SYS_kcmp is a bit of a two edged sword.
> While you mention the CONFIG issue, there is also a portability aspect
> (mesa runs on more than just linux) and as well as sandbox filtering
> of the extra syscall.
> 
> Last time I looked, the latter was still an issue and mesa was using
> SYS_kcmp to compare device node fds.
> A far shorter and more portable solution is possible, so let me
> prepare a Mesa patch.

Make sure to read my comments on 
https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6881 first. :)


-- 
Earthling Michel Dänzer               |               https://redhat.com
Libre software enthusiast             |             Mesa and X developer