linux-kernel - Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 6 May 2022 17:02:06 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     David Laight <David.Laight@...lab.com>
Cc:     "Maciej W. Rozycki" <macro@...am.me.uk>,
        Arnd Bergmann <arnd@...nel.org>, Rich Felker <dalias@...c.org>,
        "open list:IA64 (Itanium) PLATFORM" <linux-ia64@...r.kernel.org>,
        "open list:SUPERH" <linux-sh@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "open list:MIPS" <linux-mips@...r.kernel.org>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        "open list:SPARC + UltraSPARC (sparc/sparc64)" 
        <sparclinux@...r.kernel.org>,
        "open list:RISC-V ARCHITECTURE" <linux-riscv@...ts.infradead.org>,
        Will Deacon <will@...nel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Helge Deller <deller@....de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Ingo Molnar <mingo@...hat.com>,
        linux-pci <linux-pci@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Matt Turner <mattst88@...il.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Arnd Bergmann <arnd@...db.de>,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        "open list:M68K ARCHITECTURE" <linux-m68k@...ts.linux-m68k.org>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "moderated list:ARM PORT" <linux-arm-kernel@...ts.infradead.org>,
        Richard Henderson <rth@...ddle.net>,
        Michal Simek <monstr@...str.eu>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        "open list:PARISC ARCHITECTURE" <linux-parisc@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        "open list:ALPHA PORT" <linux-alpha@...r.kernel.org>,
        Borislav Petkov <bp@...en8.de>,
        "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" 
        <linuxppc-dev@...ts.ozlabs.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it
 as necessary

Hi David

On Fri, May 6, 2022 at 4:05 PM David Laight <David.Laight@...lab.com> wrote:
> From: Geert Uytterhoeven
> > Sent: 06 May 2022 14:09
> > > The same is really true for other bus type - including ISA and EISA.
> > > (Ignoring the horrid of probing ISI bus devices - hopefully they
> > > are in the ACPI tables??_
> > > If a driver is probed on a ISA bus there ought to be functions
> > > equivalent to pci_ioremap() (for both memory and IO addresses)
> > > that return tokens appropriate for the specific bus.
> > >
> > > That is all a different load of churn.
> >
> > A loooong time ago,  it was suggested to add register accessor
> > functions to struct device, so e.g. readl(dev, offset) would call
> > into these accessors, which would implement the bus-specific behavior.
> > No more worries about readl(), __raw_readl(), ioread32b(), or whatever
> > quirk is needed, at the (small on nowadays' machines) expense of
> > some indirection...
>
> I was just thinking that the access functions might need a 'device'.
> Although you also need the BAR (or equivalent).
> So readl(dev, bar_token, offset) or readl(dev, bar_token + offset).

Note that we do have such a system: regmap.

> Clearly the 'dev' parameter could be compiled out for non-DEBUG
> build on x86 - leaving the current(ish) object code.

Assumed all devices are PCI devices.
E.g. USB devices would still need the indirection.

> You don't want an indirect call (this year), but maybe real
> function call and a few tests won't make that much difference.
> They might affect PCIe writes, but PCIe reads are so slow you
> need to avoid them whenever possible.
> I've not timed reads into something like an ethernet chip,
> but into our fpga they are probably 1000 clocks+.
>
> OTOH I wouldn't want any overhead on the PIO fifo reads
> on one of our small ppc devices.
> We push a lot of data though that fifo and anything extra
> would kill performance.

Right.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds