linux-kernel - Re: [patch 00/24] x86/speculation: Remedy the STIBP/IBPB overhead

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Message-ID: <20181122094540.GL2131@hirez.programming.kicks-ass.net>
Date:   Thu, 22 Nov 2018 10:45:41 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Jiri Kosina <jkosina@...e.cz>,
        Tom Lendacky <thomas.lendacky@....com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>,
        Waiman Long <longman9394@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Dave Stewart <david.c.stewart@...el.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [patch 00/24] x86/speculation: Remedy the STIBP/IBPB overhead

On Wed, Nov 21, 2018 at 09:14:30PM +0100, Thomas Gleixner wrote:
> It's based on the x86/pti branch unfortunately, which contains the removal
> of the minimal asm retpoline hackery. I noticed too late. If the minimal
> asm stuff should not be backported it's trivial to rebase that series on
> Linus tree.

I see no problem with backporting those patches; the rationale for them
also holds for the stable trees, people really should have a retpoline
enabled compiler available by now.

Also, that minimal thing provided about as much protection as thinking
happy thoughts.