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Subject: Re: [GIT PULL 1/2] asm-generic: rework PCI I/O space access
From:   Niklas Schnelle <schnelle@linux.ibm.com>
To:     Arnd Bergmann <arnd@kernel.org>, John Garry <john.garry@huawei.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        linux-pci <linux-pci@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Date:   Fri, 03 Sep 2021 10:31:39 +0200
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On Tue, 2021-08-10 at 13:33 +0200, Arnd Bergmann wrote:
> On Tue, Aug 10, 2021 at 11:19 AM John Garry <john.garry@huawei.com> wrote:
> > On 04/08/2021 09:52, Arnd Bergmann wrote:
> > 
> > This seems a reasonable approach. Do you have a plan for this work? Or
> > still waiting for the green light?
> 
> I'm rather busy with other work at the moment, so no particular plans
> for any time soon.
> 
> > I have noticed the kernel test robot reporting the following to me,
> > which seems to be the same issue which was addressed in this series
> > originally:
> > 
> > config: s390-randconfig-r032-20210802 (attached as .config)
> > compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project
> > 4f71f59bf3d9914188a11d0c41bedbb339d36ff5)
> > ...
> > All errors (new ones prefixed by >>):
> > 
> >     In file included from drivers/block/null_blk/main.c:12:
> >     In file included from drivers/block/null_blk/null_blk.h:8:
> >     In file included from include/linux/blkdev.h:25:
> >     In file included from include/linux/scatterlist.h:9:
> >     In file included from arch/s390/include/asm/io.h:75:
> >     include/asm-generic/io.h:464:31: warning: performing pointer
> > arithmetic on a null pointer has undefined behavior
> > [-Wnull-pointer-arithmetic]
> >             val = __raw_readb(PCI_IOBASE + addr);
> > 
> > So I imagine lots of people are seeing these.
> 
> Right, this is the original problem that Niklas was trying to solve.
> 
> If Niklas has time to get this fixed, I can probably find a way to work
> with him on finishing up my proposed patch with the changes you
> suggested.
> 
>        Arnd

Sorry for the late reply, this got lost in my inbox. I could spare some
cycles on this but I'm not sure how I can help.

The series you sent after Linus' nacked the previous approach looks
quite broad touching lots of areas I have little experience with. I'd
be willing to test things and look over patches the best I can of
course.

Thanks,
Niklas