linux-kernel - Re: [RFC PATCH v2 2/6] x86/arch_prctl: add ARCH_GET_NOPTI and ARCH_SET

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Message-ID: <20180109222036.6h7jjyaayusn4yb5@pd.tnic>
Date:   Tue, 9 Jan 2018 23:20:36 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Willy Tarreau <w@....eu>
Cc:     Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Kees Cook <keescook@...omium.org>
Subject: Re: [RFC PATCH v2 2/6] x86/arch_prctl: add ARCH_GET_NOPTI and
 ARCH_SET_NOPTI to enable/disable PTI

On Tue, Jan 09, 2018 at 11:06:05PM +0100, Willy Tarreau wrote:
> That's very simple : you first know you need more perf when you see the
> name of your boss on your phone asking what's happening with the site

Ok, lemme try to understand that:

so you boot with PTI *enabled*, you don't know about the whole PTI
fiasco and the performance impact it has because you obviously live on
another planet, your boss calls you and *then* you start looking to
increase performance and *then* you google and realize, shikes, you need
to turn off PTI for a specific process. And rebooting is not an option.

Oh, and you've built the kernel with the option to be able to disable
PTI so it's not like you haven't seen it already.

Sorry but I really really don't believe that is in any way close to
reality.

If it is, then this is the story of the sysadmin who, like an ostrich,
kept his head in the sand.

:-)

-- 
Regards/Gruss,
    Boris.

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