linux-kernel - Re: [PATCH v2 00/10] x86: Clean up percpu operations

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Date:   Mon, 13 Jul 2020 15:24:16 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Brian Gerst <brgerst@...il.com>,
        Dmitry Golovin <dima@...ovin.in>,
        Alistair Delva <adelva@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH v2 00/10] x86: Clean up percpu operations

On Wed, Jul 8, 2020 at 12:36 PM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> On Mon, Jun 1, 2020 at 2:00 PM Nick Desaulniers <ndesaulniers@...gle.com> wrote:
> >
> > On Sat, May 30, 2020 at 3:11 PM Brian Gerst <brgerst@...il.com> wrote:
> > >
> > > The core percpu operations already have a switch on the width of the
> > > data type, which resulted in an extra amount of dead code being
> > > generated with the x86 operations having another switch.  This patch set
> > > rewrites the x86 ops to remove the switch.  Additional cleanups are to
> > > use named assembly operands, and to cast variables to the width used in
> > > the assembly to make Clang happy.
> >
> > Thanks for all of the work that went into this series.  I think I've
> > reviewed all of them.
> > With this series plus this hunk:
> > https://github.com/ClangBuiltLinux/continuous-integration/blob/master/patches/llvm-all/linux-next/x86/x86-support-i386-with-Clang.patch#L219-L237
> > I can build and boot i386_defconfig with Clang! So for the series:
> >
> > Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> > Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>
>
> tglx, Ingo, Boris, Linus,
> Do you all have thoughts on this series?  I can understand "let
> sleeping dogs lie" but some Android folks are really interested in
> i386 testing, and randconfigs/allnoconfigs are doing i386 builds which
> are currently broken w/ Clang. This series gets us closer to having
> test coverage of this ISA with another toolchain, FWIW.

I'm trying to organize an LLVM micro conference at plumbers.  I think
a session on "clang and remaining i386 blockers" might be of interest,
which would cover why the existing code pattern is problematic for
compiler portability.  This series in particular would be brought up.

Are you all planning on attending plumbers this year?  Might such a
session be of interest?

Otherwise, is there any additional feedback on this series or is it good to go?
-- 
Thanks,
~Nick Desaulniers