linux-kernel - Re: [PATCH v3 08/15] arm64: kvm: Split hyp/switch.c to VHE/nVHE

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Message-ID: <CAKwvOd=TswBPY7J-VH6hm80O0eq6GPA_7YUsuddwq3RHaDMQfA@mail.gmail.com>
Date:   Thu, 25 Jun 2020 11:26:18 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Will Deacon <will@...nel.org>
Cc:     Marc Zyngier <maz@...nel.org>, kernel test robot <lkp@...el.com>,
        David Brazdil <dbrazdil@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        kbuild-all@...ts.01.org,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        kvmarm@...ts.cs.columbia.edu,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>, android-kvm@...gle.com,
        Philip Li <philip.li@...el.com>
Subject: Re: [PATCH v3 08/15] arm64: kvm: Split hyp/switch.c to VHE/nVHE

On Thu, Jun 25, 2020 at 1:34 AM Will Deacon <will@...nel.org> wrote:
>
> On Thu, Jun 25, 2020 at 09:16:03AM +0100, Marc Zyngier wrote:
> > On 2020-06-25 06:03, kernel test robot wrote:
> > > Hi David,
> > >
> > > Thank you for the patch! Perhaps something to improve:
> > >
> > > [auto build test WARNING on linus/master]
> > > [also build test WARNING on v5.8-rc2 next-20200624]
> > > [cannot apply to kvmarm/next arm64/for-next/core arm-perf/for-next/perf]
> > > [If your patch is applied to the wrong git tree, kindly drop us a note.
> > > And when submitting patch, we suggest to use  as documented in
> > > https://git-scm.com/docs/git-format-patch]
> > >
> > > url:
> > > https://github.com/0day-ci/linux/commits/David-Brazdil/Split-off-nVHE-hyp-code/20200618-203230
> > > base:
> > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > > 1b5044021070efa3259f3e9548dc35d1eb6aa844
> > > config: arm64-randconfig-r021-20200624 (attached as .config)
> > > compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project
> > > 8911a35180c6777188fefe0954a2451a2b91deaf)
> > > reproduce (this is a W=1 build):
> > >         wget
> > > https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross
> > > -O ~/bin/make.cross
> > >         chmod +x ~/bin/make.cross
> > >         # install arm64 cross compiling tool for clang build
> > >         # apt-get install binutils-aarch64-linux-gnu
> > >         # save the attached .config to linux build tree
> > >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross
> > > ARCH=arm64
> > >
> > > If you fix the issue, kindly add following tag as appropriate
> > > Reported-by: kernel test robot <lkp@...el.com>
> > >
> > > All warnings (new ones prefixed by >>):
> > >
> > > > > arch/arm64/kvm/hyp/nvhe/switch.c:244:28: warning: no previous
> > > > > prototype for function 'hyp_panic' [-Wmissing-prototypes]
> > >    void __hyp_text __noreturn hyp_panic(struct kvm_cpu_context
> > > *host_ctxt)
> >
> > I really wish we could turn these warnings off. They don't add much.
> > Or is there an annotation we could stick on the function (something
> > like __called_from_asm_please_leave_me_alone springs to mind...)?
>
> Agreed, I've caught myself skim-reading the kbuild robot reports now
> because they're often just noise, and then having to force myself to look at
> them properly when I remember. Even just something in the subject to
> say "the only problems are W=1 warnings" would help. Is that possible?

When the W=1 reports started showing up, it took me a while to figure
out these warnings were only enabled at W=1.  I asked Philip to help
denote these in the reports, and Philip was kind enough to add a note
in the report about W=1.  I agree that the note could still be more
prominent.  Another part of me wants to move -Wmissing-prototypes to
W=2, but that's just biding time until 0day starts reporting on those.

-- 
Thanks,
~Nick Desaulniers