linux-kernel - RE: [RFC PATCH v2 6/6] x86/entry/pti: don't switch PGD on when pti

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Message-ID: <6590e2b183c740f6896f57ae100c2ac3@AcuMS.aculab.com>
Date:   Fri, 12 Jan 2018 16:27:44 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Linus Torvalds' <torvalds@...ux-foundation.org>,
        Willy Tarreau <w@....eu>
CC:     Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>
Subject: RE: [RFC PATCH v2 6/6] x86/entry/pti: don't switch PGD on when
 pti_disable is set

From: Linus Torvalds
> Sent: 11 January 2018 18:25
> On Thu, Jan 11, 2018 at 9:40 AM, Willy Tarreau <w@....eu> wrote:
> >> As for per-mm vs per-thread, let's make it only switchable in
> >> single-threaded processes for now and inherited when threads are
> >> created.
> >
> > That's exactly what it does for now, but Linus doesn't like it at all.
> 
> Just to clarify: I definitely want the part where it is only
> switchable in single-threaded mode, and I actually do want it
> "inherited" by threads when they do get created.
...

You need to allow for libraries that create threads before main()
is called.

	David