[PATCH] x86: Allow disabling early pci scans with pci=noearly or disallowing conf1

Some buggy systems can machine check when config space accesses
happen for some non existent devices.  i386/x86-64 do some early
device scans that might trigger this. Allow pci=noearly to disable
this. Also when type 1 is disabling also don't do any early
accesses which are always type1.

This moves the pci= configuration parsing to be a early parameter.
I don't think this can break anything because it only changes
a single global that is only used by PCI.

Cc: gregkh@suse.de
Cc: Trammell Hudson <hudson@osresearch.net>

Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 5 insertions, 1 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 71d05f48172..4ae99f6e993 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1240,7 +1240,11 @@ running once the system is up.
                                 bootloader. This is currently used on
                                 IXP2000 systems where the bus has to be
                                 configured a certain way for adjunct CPUs.
-
+                noearly         [X86] Don't do any early type 1 scanning.
+                                This might help on some broken boards which
+                                machine check when some devices' config space
+                                is read. But various workarounds are disabled
+                                and some IOMMU drivers will not work.
         pcmv=           [HW,PCMCIA] BadgePAD 4
 
         pd.             [PARIDE]