linux-kernel - Re: ERROR: modpost: "__divsi3_table" [lib/lz4/lz4

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Date:   Fri, 24 Dec 2021 04:09:27 -0800
From:   Max Filippov <jcmvbkbc@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     kernel test robot <lkp@...el.com>, kbuild-all@...ts.01.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        "open list:TENSILICA XTENSA PORT (xtensa)" 
        <linux-xtensa@...ux-xtensa.org>, Chris Zankel <chris@...kel.net>
Subject: Re: ERROR: modpost: "__divsi3_table" [lib/lz4/lz4_compress.ko] undefined!

Hi Arnd,

On Mon, Dec 6, 2021 at 3:02 AM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Mon, Dec 6, 2021 at 11:30 AM kernel test robot <lkp@...el.com> wrote:
> > First bad commit (maybe != root cause):
> > commit: 570a82b9c36f76a5959b5e47900629b0d413931d media: i2c: select V4L2_ASYNC where needed
>
> Right, that is clearly unrelated.
>
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@...el.com>
> >
> > All errors (new ones prefixed by >>, old ones prefixed by <<):
> >
> > >> ERROR: modpost: "__divsi3_table" [lib/lz4/lz4_compress.ko] undefined!
>
> lz4 was recently updated, and apparently now does a 32-bit division. I
> assume this
> is the decompressor, as arch/mips had similar problems.
>
> The possible fixes are:
>
> - disable lz4 compressed kernels on xtensa
> - change lz4 to not perform any division
> - change the xtensa decompressor to include the divsi3 helper code from the
>   main kernel, see fbf3bce45821 ("MIPS: boot/compressed/: add __ashldi3 to
>   target for ZSTD compression")

I couldn't reproduce this on xtensa with 5.16-rc6 and I don't think there
is such issue with xtensa because it has config-specific assembly
implementation of __divsi3 that doesn't use __divsi3_table.

Also the report is against nios2.

-- 
Thanks.
-- Max