From: Yijing Wang <wangyijing@huawei.com>
To: Alexey Neyman <stilor@att.net>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Bjorn Helgaas <bhelgaas@google.com>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Feng Tang <feng.tang@intel.com>, <x86@kernel.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Fix coalescing host bridge windows in arch/x86/pci/acpi.c
Date: Tue, 24 Sep 2013 11:47:21 +0800 [thread overview]
Message-ID: <52410B49.3050306@huawei.com> (raw)
In-Reply-To: <6362938.J7ZtNEOFpc@mistral>
On 2013/9/23 14:15, Alexey Neyman 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>
>
It looks fine to me, but I have no platform to test it. :)
--
Thanks!
Yijing
next prev parent reply other threads:[~2013-09-24 3:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-23 6:15 [PATCH] Fix coalescing host bridge windows in arch/x86/pci/acpi.c Alexey Neyman
2013-09-24 3:47 ` Yijing Wang [this message]
2013-09-28 7:12 ` Alexey Neyman
2013-10-03 18:44 ` Alexey Neyman
2013-10-03 19:14 ` Bjorn Helgaas
2013-10-03 23:16 ` Alexey Neyman
2013-10-09 19:30 ` Alexey Neyman
2013-10-09 23:25 ` Bjorn Helgaas
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