linux-kernel - Re: [PATCH] x86/retpoline: Fix NOSPEC

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Date:   Tue, 9 Jan 2018 17:57:11 -0800
From:   Andi Kleen <andi@...stfloor.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andi Kleen <andi@...stfloor.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Paul Turner <pjt@...gle.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Jiri Kosina <jikos@...nel.org>, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] x86/retpoline: Fix NOSPEC_JMP for tip

On Wed, Jan 10, 2018 at 02:50:12AM +0100, Thomas Gleixner wrote:
> On Tue, 9 Jan 2018, Andi Kleen wrote:
> 
> > > > I think there are areas that rely on X86_FEATURE_RETPOLINE being set
> > > > even if X86_FEATURE_RETPOLINE_AMD is set.  For example, line 261 in
> > > > arch/x86/entry/entry_32.S is only checking for X86_FEATURE_RETPOLINE.
> > > 
> > > I audited the difference places. They all seem ok.
> > 
> > Actually 32bit is not ok. For 32bit we need COMMON. So adding it.
> 
> Please keep the current X86_FEATURE_RETPOLINE as the common one and add a
> new X86_FEATURE_RETPOLINE_GENERIC which is selected by the generic/intel
> side. Little more churn, but clearer.

Ok, I just sent v2 without that. Will do a v3.

-Andi