Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary
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- To: Arnd Bergmann <arnd@xxxxxxxxxx>
- Subject: Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary
- From: "Maciej W. Rozycki" <macro@xxxxxxxxxxx>
- Date: Fri, 6 May 2022 14:16:56 +0100 (BST)
- Cc: Bjorn Helgaas <helgaas@xxxxxxxxxx>, Niklas Schnelle <schnelle@xxxxxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, linux-arch <linux-arch@xxxxxxxxxxxxxxx>, linux-pci <linux-pci@xxxxxxxxxxxxxxx>, Richard Henderson <rth@xxxxxxxxxxxxxxx>, Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>, Matt Turner <mattst88@xxxxxxxxx>, Russell King <linux@xxxxxxxxxxxxxxx>, Catalin Marinas <catalin.marinas@xxxxxxx>, Will Deacon <will@xxxxxxxxxx>, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>, Michal Simek <monstr@xxxxxxxxx>, Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>, "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>, Helge Deller <deller@xxxxxx>, Michael Ellerman <mpe@xxxxxxxxxxxxxx>, Paul Walmsley <paul.walmsley@xxxxxxxxxx>, Palmer Dabbelt <palmer@xxxxxxxxxxx>, Albert Ou <aou@xxxxxxxxxxxxxxxxx>, Yoshinori Sato <ysato@xxxxxxxxxxxxx>, Rich Felker <dalias@xxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@xxxxxxxxxx>, "open list:ALPHA PORT" <linux-alpha@xxxxxxxxxxxxxxx>, "moderated list:ARM PORT" <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>, "open list:IA64 (Itanium) PLATFORM" <linux-ia64@xxxxxxxxxxxxxxx>, "open list:M68K ARCHITECTURE" <linux-m68k@xxxxxxxxxxxxxxx>, "open list:MIPS" <linux-mips@xxxxxxxxxxxxxxx>, "open list:PARISC ARCHITECTURE" <linux-parisc@xxxxxxxxxxxxxxx>, "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" <linuxppc-dev@xxxxxxxxxxxxxxxx>, "open list:RISC-V ARCHITECTURE" <linux-riscv@xxxxxxxxxxxxxxxxxxx>, "open list:SUPERH" <linux-sh@xxxxxxxxxxxxxxx>, "open list:SPARC + UltraSPARC (sparc/sparc64)" <sparclinux@xxxxxxxxxxxxxxx>
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On Fri, 6 May 2022, Arnd Bergmann wrote:
> > So what happens if the instruction is given an I/O rather than memory BAR
> > as the relevant argument? Is the address space indicator bit (bit #0)
> > simply ignored or what?
>
> Not sure. My best guess is that it would actually work as you'd expect,
> but is deliberately left out of the architecture specification so they don't
> have to to validate the correctness. Note that only a small number of
> PCIe cards are actually supported by IBM, and I think the firmware
> only passes devices to the OS if they are whitelisted.
That makes sense, thanks!
Maciej
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