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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Tue, 8 Dec 2020 23:18:13 +0100
Message-ID: <CAK8P3a0ViH90qvr63H4J5Qn0FMfV4r9CeTHurj3N2qO2f=Dq+Q@mail.gmail.com>
Subject: Re: [PATCH] drm/amdgpu: make DRM_AMD_DC x86-only again
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        Alex Deucher <alexdeucher@gmail.com>,
        Harry Wentland <harry.wentland@amd.com>,
        Leo Li <sunpeng.li@amd.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Luben Tuikov <luben.tuikov@amd.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Mauro Rossi <issor.oruam@gmail.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Roman Li <Roman.Li@amd.com>,
        amd-gfx list <amd-gfx@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Maling list - DRI developers 
        <dri-devel@lists.freedesktop.org>,
        Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>,
        Daniel Kolesa <daniel@octaforge.org>,
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On Tue, Dec 8, 2020 at 7:21 PM 'Nick Desaulniers' via Clang Built
Linux <clang-built-linux@googlegroups.com> wrote:
>
> On Tue, Dec 8, 2020 at 6:26 AM Arnd Bergmann <arnd@kernel.org> wrote:
> >
> > On Mon, Dec 7, 2020 at 11:28 PM 'Nick Desaulniers' via Clang Built
> > Linux <clang-built-linux@googlegroups.com> wrote:
> Hmm...no warnings for me with that config on next-20201208:
> $ make LLVM=1 -j71 olddefconfig
> $ make LLVM=1 -j71
> ...
> $ clang --version
> clang version 12.0.0 (git@github.com:llvm/llvm-project.git
> 1c98f984105e552daa83ed8e92c61fba0e401410)
> (ie. near ToT LLVM)
>
> I see CONFIG_KASAN=y in the .config, so that's a recurring theme with
> clang; excessive stack usage.  It does seem a shame to disable a
> driver for a bunch of archs just due to KASAN stack usage.
> $ grep KASAN=y 0x9077925C_defconfig
> CONFIG_HAVE_ARCH_KASAN=y
> CONFIG_KASAN=y
>
> Is there a different branch of a different tree that I should be
> testing on instead? Otherwise, can you send the object file?

I was on a slightly older linux-next, and the latest version contains
the patch "ubsan: enable for all*config builds" in linux-next,
which enables CONFIG_UBSAN_SANITIZE_ALL. It took me
an hour to figure out, but after turning that option off, the warning
is back.

I'll send you the object for reference in a private mail, it's kind
of large.

        Arnd