linux-kernel - Re: [PATCH v7 0/4] Enabling Ring 3 MONITOR/MWAIT feature for Knights Landing

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Date:   Sat, 3 Dec 2016 21:27:51 +0100
From:   Pavel Machek <pavel@....cz>
To:     Grzegorz Andrejczuk <grzegorz.andrejczuk@...el.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, bp@...e.de, dave.hansen@...ux.intel.com,
        lukasz.daniluk@...el.com, james.h.cownie@...el.com,
        jacob.jun.pan@...el.com, Piotr.Luc@...el.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 0/4] Enabling Ring 3 MONITOR/MWAIT feature for Knights
 Landing

On Fri 2016-10-28 15:49:51, Grzegorz Andrejczuk wrote:
> These patches enable Intel Xeon Phi x200 feature to use MONITOR/MWAIT
> instruction in ring 3 (userspace) Patches set MSR 0x140 for all
logical CPUs.

> Then expose it as CPU feature and introduces elf HWCAP capability
>  for x86.

Elf hardware capability? Why do that? Normally CPU features go to
/proc/cpuinfo...

Plus... Can you elaborate on security effects of this? Does monitor
allow monitoring memory the current process can not write to? Is it
good idea to let userland process watch for NMIs?

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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