PCI: Add 'nodomains' boot option, and pci_domains_supported global

* Introduce pci_domains_supported global, hardcoded to zero if
  !CONFIG_PCI_DOMAINS.

* Introduce 'nodomains' boot option, which clears pci_domains_supported
  on platforms that enable it by default (x86, x86-64, and others when
  they are converted to use this).

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index e9acd5540d29..d006e8b66ffa 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1274,6 +1274,8 @@ and is between 256 and 4096 characters. It is defined in the file
                 noaer           [PCIE] If the PCIEAER kernel config parameter is
                                 enabled, this kernel boot option can be used to
                                 disable the use of PCIE advanced error reporting.
+                nodomains       [PCI] Disable support for multiple PCI
+                                root domains (aka PCI segments, in ACPI-speak).
                 nommconf        [X86-32,X86_64] Disable use of MMCONFIG for PCI
                                 Configuration
                 nomsi           [MSI] If the PCI_MSI kernel config parameter is