USB3 prevents bootup

[Hexorg]

I have a very peculiar problem. It seems like my USB3 driver is preventing a bootup. It's odd though because sometime plugging devices in USB2 or 3 will fix the problem, but then on the next reboot it'll come up again.

What happens is my kernel will boot and start init.rc scripts. It'll reach a point right before starting xorg, and I'll see a ton of print_k() output about xhci_hcd. At this point I won't be able to do anything but hard reset even though I never saw a kernel panic. I can't seem to pinpoint at what exactly is causing the issue.

I managed to get the dmesg output with syslog-ng, but It was a bit too late at capturing the whole log: https://gist.github.com/73de783f3f572404f365

My .config for kernel 3.12.20-gentoo: https://gist.github.com/e4cd8bb0452f5c9fc35e

lspci: https://gist.github.com/baaea1c785fc40ef15b5

lsusb: https://gist.github.com/f7f1de4a045acc90b9ce

[DONAHUE]

http://unix.stackexchange.com/questions/72625/why-is-usb-not-working-in-linux-when-it-works-in-uefi-bios also on this forum somewhere but my search fails to find it

Extracting:

It seems with newer Gigabyte mainboards (at least) there is a BIOS option called IOMMU Controller that is disabled by default and gives no clue or indication as to what it is for.
Enabling this setting and rebooting "magically" restores all my USB and networking problems in a 64-bit Linux OS (doesn't matter which one).

What did help, though, was adding "iommu=soft" to the kernel command line.

or " iommu=pt"
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