linux-kernel - Re: [PATCH v2] x86: bring back rep movsq for user access on CPUs without ERMS

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Message-ID: <CAHk-=whnEF7-+DL+71wVgnJG1xjeHAQjzqMAULgQq_uhWfP0ZA@mail.gmail.com>
Date:   Sun, 3 Sep 2023 20:17:53 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Mateusz Guzik <mjguzik@...il.com>
Cc:     Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, bp@...en8.de
Subject: Re: [PATCH v2] x86: bring back rep movsq for user access on CPUs
 without ERMS

On Sun, 3 Sept 2023 at 20:07, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Try it and you'll see it is not even *remotely* as easy as you claim.
> Not when you have to deal with random sizes and padding of 20+
> different architectures.

Perhaps more importantly, nobody actually seems to have the energy to care.

As shown by the fact that even the current really simple "just define
INIT_STRUCT_STAT_PADDING to avoid a pointless memset in a hot path"
has been taken up by exactly zero other architectures than x86.

I wasn't going to fight that kind of history of apathy.

              Linus