linux-kernel - Re: [PATCH] kbuild, x86: revert macros in extended asm workarounds

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Date:   Sat, 15 Dec 2018 09:51:12 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        Richard Biener <rguenther@...e.de>,
        Nadav Amit <namit@...are.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-sparse@...r.kernel.org, Alok Kataria <akataria@...are.com>,
        Juergen Gross <jgross@...e.com>,
        Andy Lutomirski <luto@...nel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH] kbuild, x86: revert macros in extended asm workarounds

Hi Peter,

On Thu, Dec 13, 2018 at 7:53 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Thu, Dec 13, 2018 at 06:17:41PM +0900, Masahiro Yamada wrote:
> > Revert the following commits:
> >
> > - 5bdcd510c2ac9efaf55c4cbd8d46421d8e2320cd
> >   ("x86/jump-labels: Macrofy inline assembly code to work around GCC inlining bugs")
> >
> > - d5a581d84ae6b8a4a740464b80d8d9cf1e7947b2
> >   ("x86/cpufeature: Macrofy inline assembly code to work around GCC inlining bugs")
> >
> > - 0474d5d9d2f7f3b11262f7bf87d0e7314ead9200.
> >   ("x86/extable: Macrofy inline assembly code to work around GCC inlining bugs")
> >
> > - 494b5168f2de009eb80f198f668da374295098dd.
> >   ("x86/paravirt: Work around GCC inlining bugs when compiling paravirt ops")
> >
> > - f81f8ad56fd1c7b99b2ed1c314527f7d9ac447c6.
> >   ("x86/bug: Macrofy the BUG table section handling, to work around GCC inlining bugs")
> >
> > - 77f48ec28e4ccff94d2e5f4260a83ac27a7f3099.
> >   ("x86/alternatives: Macrofy lock prefixes to work around GCC inlining bugs")
> >
> > - 9e1725b410594911cc5981b6c7b4cea4ec054ca8.
> >   ("x86/refcount: Work around GCC inlining bug")
> >   (Conflicts: arch/x86/include/asm/refcount.h)
> >
> > - c06c4d8090513f2974dfdbed2ac98634357ac475.
> >   ("x86/objtool: Use asm macros to work around GCC inlining bugs")
> >
> > - 77b0bf55bc675233d22cd5df97605d516d64525e.
> >   ("kbuild/Makefile: Prepare for using macros in inline assembly code to work around asm() related GCC inlining bugs")
> >
>
> I don't think we want to blindly revert all that. Some of them actually
> made sense and did clean up things irrespective of the asm-inline issue.
>
> In particular I like the jump-label one.

[1] The #error message is unnecessary.

[2] keep STATC_BRANCH_NOP/JMP instead of STATIC_JUMP_IF_TRUE/FALSE



In v2, I will make sure to not re-add [1].
I am not sure about [2].


Do you mean only [1],
or both of them?



> The cpufeature one OTOh, yeah,
> I'd love to get that reverted.
>
> And as a note; the normal commit quoting style is:
>
>   d5a581d84ae6 ("x86/cpufeature: Macrofy inline assembly code to work around GCC inlining bugs")


OK. I will do so in v2.


--
Best Regards
Masahiro Yamada