Re: [GIT pull] x86 mpx support for 3.19

From: Linus Torvalds
Date: Wed Dec 10 2014 - 14:50:08 EST

On Wed, Dec 10, 2014 at 11:41 AM, Dave Hansen
<dave.hansen@xxxxxxxxxxxxxxx> wrote:
> But, this is the kind of option that we want to be *sure* is enabled
> unless folks know exactly what they are doing, so we should probably
> hide it behind CONFIG_EXPERT as well, just as SMEP is.

I disagree.

SMEP doesn't have any performance overhead, and SMEP is available in
processors available today. So SMEP doesn't even have a config option,
because there is no downside with having it on and enabled.

MPX, in contrast, you don't even normally want to run at all as a
normal user because of the overheads. That's going to be true even
when it's available.

So I would claim the exact reverse: right now, enabling MPX should be
something only experts should do.

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