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; } } }