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

From: Alexey Neyman
Date: Mon Sep 16 2013 - 12:42:01 EST


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.
--- 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;
}
}
}