Yu,We had reported more details @
https://bugzilla.redhat.com/show_bug.cgi?id=479996 and
http://bugzilla.kernel.org/show_bug.cgi?id=11821
Look into http://bugzilla.kernel.org/show_bug.cgi?id=11821
and find that:
wlan0: Failed to config new SSID to the low-level driver
BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
IP: [<ffffffff8037cf1f>] pci_find_upstream_pcie_bridge+0x1f/0xa0
...
[<ffffffff80386808>] get_domain_for_dev+0x58/0x620
[<ffffffff8029574d>] ? __alloc_pages_internal+0xed/0x4f0
[<ffffffff803870f8>] get_valid_domain_for_dev+0x18/0x150
[<ffffffff803875e7>] intel_map_single+0x47/0x160
[<ffffffff802b8726>] ? alloc_pages_current+0x76/0xf0
[<ffffffff8038777f>] intel_alloc_coherent+0x7f/0xb0
...
Wireless LAN could cause the NULL pointer access in get_domain_for_dev() which is IOMMU function.
As an experiment, could you disable wireless lan on your machine and try to boot IOMMU kernel?
Thanks.
-Fenghua