linux-kernel - Re: [PATCH] [RFC] x86: work around MPX Erratum

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Message-ID: <CA+55aFycv2=xwDYZS9yPLcrBY7EW=o9xAO9rJPkyw6tkkf_emQ@mail.gmail.com>
Date:	Tue, 3 May 2016 14:33:01 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Dave Hansen <dave.hansen@...el.com>
Cc:	Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Andy Lutomirski <luto@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] [RFC] x86: work around MPX Erratum

On Tue, May 3, 2016 at 2:28 PM, Dave Hansen <dave.hansen@...el.com> wrote:
>>
>> So we won't init MPX on those...
>
> Yes, and as long as such a processor doesn't exist today and never
> exists in the future or the folks that buy such a processor truly don't
> care about MPX, that's fine to do.  I'm just a bit nervous about the
> whole "never exists in the future" part.

I don't think we need to care.

If a CPU doesn't support SMEP, there really is no reason for us to
ever support MPX either.

It's not like there is a clamoring for MPX support in the first place
(have you ever heard of anybody actually asking for or using it?), and
quite frankly, it's a _lot_ more complicated from a CPU core side than
SMEP (which is trivial).

So if Intel ever releases a CPU with MPX but without SMEP, nobody will
ever care about the MPX part being useless.

                 Linus