linux-kernel - Re: [PATCH 1/2] x86: Simplify Retpoline thunk

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Message-ID: <20220420152736.qzl3nikds6mq5nrr@treble>
Date:   Wed, 20 Apr 2022 08:27:36 -0700
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, brgerst@...il.com, jiangshanlai@...il.com,
        Andrew.Cooper3@...rix.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] x86: Simplify Retpoline thunk

On Tue, Apr 19, 2022 at 10:41:10PM +0200, Peter Zijlstra wrote:
> Now that we rewrite all the indirect call sites, per commit:
> 
>   750850090081 ("x86/alternative: Implement .retpoline_sites support")
> 
> it doesn't make sense to have the retpoline thunks be an ALTERNATIVE_2
> that still includes a 'naked' indirect jump.
> 
> (this accidentally 'defunnels' i386 by going back to full retpolines)

So mitigations=off no longer works on i386?

Is funneling even a concern on i386?  I don't think it has eIBRS anyway,
or does it?

-- 
Josh