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

[Alexey Neyman <stilor@att.net>]

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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.

[-- Attachment #2: acpi.c.diff --]
[-- Type: text/x-patch, Size: 633 bytes --]

--- arch/x86/pci/acpi.c.orig	2013-09-12 16:23:06.113813150 -0700
+++ arch/x86/pci/acpi.c	2013-09-12 16:23:56.605813117 -0700
@@ -357,12 +357,12 @@
 			 * the kernel resource tree doesn't allow overlaps.
 			 */
 			if (resource_overlaps(res1, res2)) {
-				res1->start = min(res1->start, res2->start);
-				res1->end = max(res1->end, res2->end);
+				res2->start = min(res1->start, res2->start);
+				res2->end = max(res1->end, res2->end);
 				dev_info(&info->bridge->dev,
 					 "host bridge window expanded to %pR; %pR ignored\n",
-					 res1, res2);
-				res2->flags = 0;
+					 res2, res1);
+				res1->flags = 0;
 			}
 		}
 	}