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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Fri, 17 Dec 2021 15:32:59 +0100
Message-ID: <CAK8P3a0dnXX7Cx_kJ_yLAoQFCxoM488Ze-L+5v1m0YeyjF4zqw@mail.gmail.com>
Subject: Re: [GIT PULL 1/2] asm-generic: rework PCI I/O space access
To:     John Garry <john.garry@huawei.com>
Cc:     Niklas Schnelle <schnelle@linux.ibm.com>,
        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>
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On Fri, Dec 17, 2021 at 3:27 PM John Garry <john.garry@huawei.com> wrote:
> On 17/12/2021 13:52, Niklas Schnelle wrote:
> >>> I have tested this on s390 with HAS_IOPORT=3Dn and allyesconfig as we=
ll
> >>> as running it with defconfig. I've also been using it on my Ryzen 399=
0X
> >>> workstation with LEGACY_PCI=3Dn for a few days. I do get about 60 MiB
> >>> fewer modules compared with a similar config of v5.15.8. Hard to say
> >>> which other systems might miss things of course.
> >>>
> >>> I have not yet worked on the discussed IOPORT_NATIVE flag. Mostly I'm
> >>> wondering two things. For one it feels like that could be a separate
> >>> change on top since HAS_IOPORT + LEGACY_PCI is already quite big.
> >>> Secondly I'm wondering about good ways of identifying such drivers an=
d
> >>> how much this overlaps with the ISA config flag.
>
> I was interesting in the IOPORT_NATIVE flag (or whatever we call it) as
> it solves the problem of drivers which "unconditionally do inb()/outb()
> without checking the validity of the address using firmware or other
> methods first" being built for (and loaded on and crashing) unsuitable
> systems. Such a problem is in [0]
>
> So if we want to support that later, then it seems that someone would
> need to go back and re-edit many same driver Kconfigs =E2=80=93 like hwon=
, for
> example. I think it's better to avoid that and do it now.
>
> Arnd, any opinion on that?
>
> I'm happy to help with that effort.

I looked at the options the other day and couldn't really find any that
fell into this category, so I suggested that Niklas would skip that for the
moment. If you have a better way of finding the affected drivers,
that would be great.

       Arnd