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Date:   Sat, 25 Apr 2020 20:53:13 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Segher Boessenkool <segher@kernel.crashing.org>
Cc:     Arvind Sankar <nivedita@alum.mit.edu>,
        Jakub Jelinek <jakub@redhat.com>, jgross@suse.com,
        x86@kernel.org, Kees Cook <keescook@chromium.org>,
        Peter Zijlstra <peterz@infradead.org>,
        linuxppc-dev@lists.ozlabs.org, Michael Matz <matz@suse.de>,
        Nick Desaulniers <ndesaulniers@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Sergei Trofimovich <slyfox@gentoo.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Ingo Molnar <mingo@redhat.com>,
        Paul Mackerras <paulus@samba.org>,
        Andy Lutomirski <luto@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
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        <frederic.pierret@qubes-os.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Martin =?utf-8?B?TGnFoWth?= <mliska@suse.cz>,
        boris.ostrovsky@oracle.com
Subject: Re: [PATCH] x86: Fix early boot crash on gcc-10, next try
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On Sat, Apr 25, 2020 at 01:37:01PM -0500, Segher Boessenkool wrote:
> That is a lot more typing then
> 	asm("");

That's why a macro with a hopefully more descriptive name would be
telling more than a mere asm("").

> but more seriously, you probably should explain why you do not want a
> tail call *anyway*, and in such a comment you can say that is what the
> asm is for.

Yes, the final version will have a comment and the whole spiel. This
diff is just me polling the maintainers: "do you want this for your arch
too?" Well, the PPC maintainers only, actually.

The other call in init/main.c would be for everybody.

> I don't see anything that prevents the tailcall in current code either,
> fwiw.

Right, and I don't see a reason why gcc-10 would do that optimization on
x86 only but I better ask first.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette