linux-kernel - Re: [patch V2 00/28] x86/speculation: Remedy the STIBP/IBPB overhead

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Message-ID: <20181126133739.GC108014@gmail.com>
Date:   Mon, 26 Nov 2018 14:37:39 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.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>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        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 V2 00/28] x86/speculation: Remedy the STIBP/IBPB overhead


* Thomas Gleixner <tglx@...utronix.de> wrote:

> Thats hopefully the final version of this. Changes since V1:
> 
>   - Renamed the command line option and related code to spectre_v2_user= as
>     suggested by Josh.
> 
>   - Thought more about the back to back optimization and finally left the
>     IBPB code in switch_mm().
> 
>     It still removes the ptrace check for the always IBPB case. That's
>     substantial overhead for dubious value now that the default is
>     conditional (prctl/seccomp) IBPB.
> 
>   - Added two options which allow conditional STIBP and IBPB always mode.
> 
>   - Addressed the review comments

With the typo review feedback outlined in the discussions:

Reviewed-by: Ingo Molnar <mingo@...nel.org>

Thanks,

	Ingo