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From:   Marco Elver <elver@google.com>
Date:   Thu, 9 Sep 2021 12:53:03 +0200
Message-ID: <CANpmjNNCVu8uyn=8=5_8rLeKM5t3h7-KzVg1aCJASxF8u_6tEQ@mail.gmail.com>
Subject: Re: [PATCH] Enable '-Werror' by default for all kernel builds
To:     Christoph Hellwig <hch@infradead.org>
Cc:     Guenter Roeck <linux@roeck-us.net>,
        Nathan Chancellor <nathan@kernel.org>,
        Arnd Bergmann <arnd@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        llvm@lists.linux.dev, Nick Desaulniers <ndesaulniers@google.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        linux-riscv@lists.infradead.org,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        kasan-dev@googlegroups.com,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        "Pan, Xinhui" <Xinhui.Pan@amd.com>, amd-gfx@lists.freedesktop.org
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On Thu, 9 Sept 2021 at 07:59, Christoph Hellwig <hch@infradead.org> wrote:
> On Wed, Sep 08, 2021 at 11:58:56PM +0200, Marco Elver wrote:
> > It'd be good to avoid. It has helped uncover build issues with KASAN in
> > the past. Or at least make it dependent on the problematic architecture=
.
> > For example if arm is a problem, something like this:
>
> I'm also seeing quite a few stack size warnings with KASAN on x86_64
> without COMPILT_TEST using gcc 10.2.1 from Debian.  In fact there are a
> few warnings without KASAN, but with KASAN there are a lot more.
> I'll try to find some time to dig into them.

Right, this reminded me that we actually at least double the real
stack size for KASAN builds, because it inherently requires more stack
space. I think we need Wframe-larger-than to match that, otherwise
we'll just keep having this problem:

https://lkml.kernel.org/r/20210909104925.809674-1-elver@google.com

> While we're at it, with -Werror something like this is really futile:
>
> drivers/gpu/drm/amd/amdgpu/amdgpu_object.c: In function =E2=80=98amdgpu_b=
o_support_uswc=E2=80=99:
> drivers/gpu/drm/amd/amdgpu/amdgpu_object.c:493:2: warning: #warning
> Please enable CONFIG_MTRR and CONFIG_X86_PAT for better performance thank=
s to write-combining [-Wcpp
>   493 | #warning Please enable CONFIG_MTRR and CONFIG_X86_PAT for better =
performance \
>       |  ^~~~~~~