linux-kernel - Re: [PATCH] x86: bring back rep movsq for user access on CPUs without ERMS

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Message-ID: <CAGudoHGGXNP5dBpZLadBUTVeD-JPEuikQXONruJzvnRJrp5+KA@mail.gmail.com>
Date:   Mon, 28 Aug 2023 20:04:52 +0200
From:   Mateusz Guzik <mjguzik@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        bp@...en8.de
Subject: Re: [PATCH] x86: bring back rep movsq for user access on CPUs without ERMS

On 8/28/23, Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> On Mon, 28 Aug 2023 at 10:07, Mateusz Guzik <mjguzik@...il.com> wrote:
>>
>> While here make sure labels are unique.
>
> I'll take a look at the other changes later, but this one I reacted
> to: please don't do this.
>
> It's a disaster. It makes people make up random numbers, and then
> pointlessly change them if the code moves around etc.
>
> Numeric labels should make sense *locally*.  The way to disambiguate
> them is to have each use just have "f" and 'b" to distinguish whether
> it refers forward or backwards.
>
[snip]

Other files do it (e.g., see __copy_user_nocache), but I have no
strong opinion myself.

That said I'll wait for the rest of the review before sending a v2.

-- 
Mateusz Guzik <mjguzik gmail.com>