x86/PCI: don't fall back to defaults if _CRS has no apertures

Host bridges that lead to things like the Uncore need not have any
I/O port or MMIO apertures.  For example, in this case:

    ACPI: PCI Root Bridge [UNC1] (domain 0000 [bus ff])
    PCI: root bus ff: using default resources
    PCI host bridge to bus 0000:ff
    pci_bus 0000:ff: root bus resource [io  0x0000-0xffff]
    pci_bus 0000:ff: root bus resource [mem 0x00000000-0x3fffffffffff]

we should not pretend those default resources are available on bus ff.

CC: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
index a312e76063a7..daa42490c1d9 100644
--- a/arch/x86/pci/acpi.c
+++ b/arch/x86/pci/acpi.c
@@ -404,7 +404,12 @@ struct pci_bus * __devinit pci_acpi_scan_root(struct acpi_pci_root *root)
                 kfree(sd);
         } else {
                 get_current_resources(device, busnum, domain, &resources);
-                if (list_empty(&resources))
+
+                /*
+                 * _CRS with no apertures is normal, so only fall back to
+                 * defaults or native bridge info if we're ignoring _CRS.
+                 */
+                if (!pci_use_crs)
                         x86_pci_root_bus_resources(busnum, &resources);
                 bus = pci_create_root_bus(NULL, busnum, &pci_root_ops, sd,
                                           &resources);