From: Alexey Neyman <stilor@att.net>
To: Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [PATCH] Fix coalescing host bridge windows in arch/x86/pci/acpi.c
Date: Wed, 9 Oct 2013 12:30:10 -0700
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Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Feng Tang <feng.tang@intel.com>, Yijing Wang <wangyijing@huawei.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <6362938.J7ZtNEOFpc@mistral> <CAErSpo6XCu4ROJCh5=+7zwupjbtobowoNeF1PcXEvdg349C_pg@mail.gmail.com> <201310031616.08617.stilor@att.net>
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[Patch ping #5]

On Thursday, October 03, 2013 04:16:07 pm Alexey Neyman wrote:
> On Thursday, October 03, 2013 12:14:38 pm Bjorn Helgaas wrote:
> > On Mon, Sep 23, 2013 at 12:15 AM, Alexey Neyman <stilor@att.net> wrote:
> > > [Resending due to no response to the original message in a week]
> > > 
> > > Hi all,
> > > 
> > > I have a board with a BIOS bug that reports the following I/O port
> > > regions in _CRS on one of the host bridges:
> > > 
> > > 0x0000-0x03af // #0
> > > 0x03e0-0x0cf7 // #1
> > > 0x03b0-0x03bb // #2
> > > 0x03c0-0x03df // #3
> > > 0x0000-0xdfff // #4
> > > 0xf000-0xffff // #5
> > > 
> > > Obviously, region number #4 is erroneous as it overlaps with regions
> > > #0..3. The code in coalesce_windows() in arch/x86/pci/acpi.c attempts
> > > to recover from such kind of BIOS bugs by merging the overlapping
> > > regions. Current code expands region #0 to 0x0000-0xdffff and makes
> > > region #4 ignored. As a result, overlap of the expanded region #0 with
> > > regions #1..3 remains undetected (as the inner loop already compared
> > > them with region #0). As a result, regions #1..3 are inserted into the
> > > resource tree even though they overlap with adjusted region #0 - which
> > > later results in resource conflicts for PCI devices with IO ports in
> > > one of those regions (e.g., for an PCI IDE controller in legacy mode -
> > > which has port 0x3f6). The kernel then refuses to initialize these
> > > devices.
> > > 
> > > The fix: instead of expanding res1 and ignoring res2, do the opposite.
> > > The res2 window is yet to be compared against all windows between res1
> > > and res2 (regions #1..3 in the above example), so the resulting
> > > resource map will include just the expanded region - and will ignore
> > > any overlapping ones.
> > > 
> > > Signed-off-by: Alexey Neyman <stilor@att.net>
> > 
> > Can you please open a report at http://bugzilla.kernel.org, assign it
> > to drivers/pci, and attach a complete dmesg log?
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=62511
> 
> I am not at liberty to disclose full hardware configuration of the board,
> as it is a proprietary prototype board not in production. I've provided
> the relevant messages from dmesg though.

Could anybody review/commit?

Regards,
Alexey.
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