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

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Message-ID: <5636839.b8jCOluuC9@mistral>
Date:	Sat, 28 Sep 2013 00:12:48 -0700
From:	Alexey Neyman <stilor@....net>
To:	Yijing Wang <wangyijing@...wei.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Feng Tang <feng.tang@...el.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix coalescing host bridge windows in arch/x86/pci/acpi.c

On Tuesday, September 24, 2013 11:47:21 AM Yijing Wang wrote:
> 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@....net>
> 
> It looks fine to me, but I have no platform to test it. :)

Thanks for a review. Could anybody push it into the tree? :)
For convenience, patch attached again.

Regards,
Alexey.
View attachment "acpi.c.diff" of type "text/x-patch" (723 bytes)