linux-kernel - Re: [PATCH] x86/nospec: Fixup array_index_nospec

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Message-ID: <CAPcyv4hZjYh2eTiDWV1NTdoDoNMZa8YM21CSqmh+jwhObZjf6Q@mail.gmail.com>
Date:   Tue, 6 Feb 2018 17:55:36 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86/nospec: Fixup array_index_nospec_mask() asm constraint

On Tue, Feb 6, 2018 at 5:50 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Tue, Feb 6, 2018 at 5:33 PM, Dan Williams <dan.j.williams@...el.com> wrote:
>> Allow the compiler to handle @size as an immediate value rather than
>> allocating a register.
>
> Actually, maybe that "ir" should be "g".
>
> Because it's fine if it's a memory location too. "cmp" takes pretty
> much anything, as long as the thing we compare _to_ is a register.

Ok, no worries I'll do a v2. In fact you suggested 'g' in your initial
version and I lost that along the way while wrestling with why the
compiler miscompiled it until I put it in a static inline rather than
a macro.