linux-kernel - Re: [PATCH PING] Fix coalescing of host bridge windows in arch/x86/pci/acpi.c

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Message-Id: <201309160941.54844.stilor@att.net>
Date:	Mon, 16 Sep 2013 09:41:54 -0700
From:	Alexey Neyman <stilor@....net>
To:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH PING] Fix coalescing of host bridge windows in arch/x86/pci/acpi.c

Hi all,

Could anybody review/commit the patch?

Regards,
Alexey.

On Thursday, September 12, 2013 05:19:16 pm Alexey Neyman wrote:
> 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.
> However, 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 a result, regions #1..3 are inserted into the
> resource tree as if they were consumers of the 0x0000-0xdfff regions, and
> devices that have resources in one of these regions (e.g. 0x3f6 for legacy
> IDE) have a resource conflict - the kernel does not initialize them.
> 
> The attached patch makes the code in coalesce_windows() instead ignore res1
> (which is already dealt with), possibly expanding res2 instead. As res2 has
> not been reached in the outer loop in coalesce_windows(), the code will
> then check for overlaps of the just-expanded resource with the rest of the
> resources.
> 
> Regards,
> Alexey.

View attachment "acpi.c.diff" of type "text/x-patch" (634 bytes)