linux-kernel - Re: [PATCH] x86/retpoline: Avoid return buffer underflows on context switch

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Message-ID: <1515453935.4423.46.camel@amazon.co.uk>
Date:   Mon, 8 Jan 2018 23:25:35 +0000
From:   "Woodhouse, David" <dwmw@...zon.co.uk>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     "andi@...stfloor.org" <andi@...stfloor.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tim.c.chen@...ux.intel.com" <tim.c.chen@...ux.intel.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "pjt@...gle.com" <pjt@...gle.com>,
        "dave.hansen@...el.com" <dave.hansen@...el.com>,
        "luto@...capital.net" <luto@...capital.net>,
        "gregkh@...ux-foundation.org" <gregkh@...ux-foundation.org>
Subject: Re: [PATCH] x86/retpoline: Avoid return buffer underflows on
 context switch

On Mon, 2018-01-08 at 23:26 +0100, Peter Zijlstra wrote:
> 
> > is because that might get interpreted as a "push %rip" and not go on
> > the RSB at all. Hence the 'pause' between each one.
> 
> OK, then make the comment say that.

Fixed. I've also shifted the #ifdef CONFIG_RETPOLINE to the call sites
instead of inside the FILL_RETURN_BUFFER macro itself. This is going to
get used with IBRS code too, Real Soon Now™.

http://git.infradead.org/users/dwmw2/linux-retpoline.git/commitdiff/6e961b86558
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