Messages in this thread | | | From | John Garry <> | Subject | Re: [GIT PULL 1/2] asm-generic: rework PCI I/O space access | Date | Tue, 21 Dec 2021 16:21:10 +0000 |
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On 19/12/2021 14:23, David Laight wrote: >>>>> I have tested this on s390 with HAS_IOPORT=n and allyesconfig as well >>>>> as running it with defconfig. I've also been using it on my Ryzen 3990X >>>>> workstation with LEGACY_PCI=n 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 and >>>>> 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 – like hwmon, for >> example. I think it's better to avoid that and do it now. > Could you do something where valid arguments to inb() have to come > from some kernel mapping/validation function and are never in the > range [0x0, 0x10000). > Then drivers that are cheating the system will fail.
That sounds like the solution which I had here:
https://lore.kernel.org/lkml/1610729929-188490-2-git-send-email-john.garry@huawei.com/
It worked for the scenario I was interested in, but Arnd had some concerns, which you can check there.
> > Or, maybe, only allow [0x0, 0x10000) on systems that have a suitable bus. > With the mapping functions returning a different value (eg the KVA into > the PCI master window) that can be separately verified. > That would let drivers do (say) inb(0x120) on systems that have (something > like) and ISA bus, but not on PCI-only systems which support PCI IO > accesses through a physical address window.
I'm not sure how this would look in practice. What would the check for the suitable bus be?
Thanks, John
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