linux-kernel - Re: [PATCH] x86/alternatives: Fix optimize

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Message-ID: <CA+55aFykL6+9kJjP2J-y3D7h7s3KhASVJ_cULa12zk5o37=OsA@mail.gmail.com>
Date:   Wed, 10 Jan 2018 13:05:08 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Woodhouse <dwmw2@...radead.org>,
        Andi Kleen <andi@...stfloor.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Paul Turner <pjt@...gle.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        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/alternatives: Fix optimize_nops() checking

On Wed, Jan 10, 2018 at 12:55 PM, Borislav Petkov <bp@...en8.de> wrote:
>
> Ok, so the problem was: how to fixup jumps which are not the first
> instruction which is being replaced but a following one in the
> instruction bytes with which we replace.

What jumps do you have that need to be fixed up?

I really think we should avoid having things like that.

Any jumps *within* the alternatives should have been handled by the
assembler already.

And jumps between the alternatives and other places? Why do they exist?

            Linus