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

From: Mateusz Guzik
Date: Mon Aug 28 2023 - 14:05:29 EST


On 8/28/23, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, 28 Aug 2023 at 10:07, Mateusz Guzik <mjguzik@xxxxxxxxx> 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>