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Date:   Mon, 04 Dec 2023 14:50:45 +0100
From:   "Arnd Bergmann" <arnd@arndb.de>
To:     "Philipp Stanner" <pstanner@redhat.com>,
        "Bjorn Helgaas" <bhelgaas@google.com>,
        "Hanjun Guo" <guohanjun@huawei.com>, "Neil Brown" <neilb@suse.de>,
        "Kent Overstreet" <kent.overstreet@gmail.com>,
        "Jakub Kicinski" <kuba@kernel.org>,
        "Niklas Schnelle" <schnelle@linux.ibm.com>,
        "Uladzislau Koshchanka" <koshchanka@gmail.com>,
        "John Sanpe" <sanpeqf@gmail.com>,
        "Dave Jiang" <dave.jiang@intel.com>,
        "Masami Hiramatsu" <mhiramat@kernel.org>,
        "Kees Cook" <keescook@chromium.org>,
        "David Gow" <davidgow@google.com>,
        "Herbert Xu" <herbert@gondor.apana.org.au>,
        "Shuah Khan" <skhan@linuxfoundation.org>,
        "wuqiang.matt" <wuqiang.matt@bytedance.com>,
        "Yury Norov" <yury.norov@gmail.com>,
        "Jason Baron" <jbaron@akamai.com>,
        "Andrew Morton" <akpm@linux-foundation.org>,
        "Ben Dooks" <ben.dooks@codethink.co.uk>,
        "Danilo Krummrich" <dakr@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
        Linux-Arch <linux-arch@vger.kernel.org>, stable@vger.kernel.org,
        "Arnd Bergmann" <arnd@kernel.org>
Subject: Re: [PATCH v3 5/5] lib, pci: unify generic pci_iounmap()
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On Mon, Dec 4, 2023, at 14:39, Philipp Stanner wrote:
> On Mon, 2023-12-04 at 13:38 +0100, Philipp Stanner wrote:

>> + */
>> +#if defined(ARCH_WANTS_GENERIC_IOMEM_IS_IOPORT)
>> +bool iomem_is_ioport(void __iomem *addr)
>> =C2=A0{
>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0IO_COND(addr, /* nothing *=
/, iounmap(addr));
>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0unsigned long port =3D (un=
signed long __force)addr;
>> +
>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (port > PIO_OFFSET && p=
ort < PIO_RESERVED)
>
> by the way:
> Reading that again my instinctive feeling would be that it should be
> port >=3D PIO_OFFSET.
>
> This is, however, the exactly copied logic from the IO_COND macro in
> lib/iomap.c. Is it possible that this macro contains a bug here?

Right, I think that would make more sense, but there is no
practical difference as long as I/O port 0 is always unused,
which is at least true on x86 because of PCIBIOS_MIN_IO.
Commit bb356ddb78b2 ("RISC-V: PCI: Avoid handing out address
0 to devices") describes how setting PCIBIOS_MIN_IO to 0
caused other problems.

I would just leave the logic consistent with IO_COND here,
or maybe use IO_COND() directly, like

      IO_COND(addr, return true, /* nothing */);
      return false;

     Arnd