linux-kernel - Re: [PATCH 03/24] x86/paravirt: Annotate indirect calls

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Date:   Thu, 25 Jan 2018 10:02:05 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Jason Baron <jbaron@...mai.com>
Subject: Re: [PATCH 03/24] x86/paravirt: Annotate indirect calls

On Tue, 2018-01-23 at 16:25 +0100, Peter Zijlstra wrote:
> Paravirt emits indirect calls which get flagged by objtool retpoline
> checks, annotate it away because all these indirect calls will be
> patched out before we start userspace.

I've seen this asserted repeatedly but I've never truly convinced
myself of it. Is this absolutely unconditionally true in every case,
even when we're running as a guest and there are *actual* calls to be
made? We turn them into direct calls, never leave them indirect?
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