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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Tue, 27 Sep 2022 10:03:51 -0700
Message-ID: <CAKwvOd=a+0VNP-d=mHnbM4ujdtPrujru4dxHtfDo+EEM+b6deg@mail.gmail.com>
Subject: Re: [PATCH] x86, mem: move memmove to out of line assembler
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Kees Cook <keescook@chromium.org>,
        linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
        Andy Lutomirski <luto@kernel.org>
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Oh, yeah my patch essentially _is_
commit 9599ec0471de ("x86-64, mem: Convert memmove() to assembly file
and fix return value bug")
but for 32b (and no return value bug).  I should probably amend a
reference to that in the commit message for this patch.

Also, I'm missing an EXPORT_SYMBOL in my v1, so modules that reference
memmove will fail to build during modpost. v2 is required.

On Fri, Sep 23, 2022 at 11:06 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> But I'm looking at that x86-64 memcpy_orig, and I think it looks
> fairly good as a template for doing the same on x86-32. And we could
> get rid of the duplication on the x86-64 side.

Is the suggestion that 64b memcpy_orig could be replaced with __memmove?

Sorry, I'm not sure I follow either suggestions for code reuse opportunities.

Also, any ideas which machines for QEMU don't have ERMS for testing
these non-ERMS implementations?

>
> That said, your patch looks fine too, as a "minimal changes" thing.
>
>                 Linus

--
Thanks,
~Nick Desaulniers