190.42 with virtualization on Dell E6500 AMD64 results in black screen

[marisn]

When enabling virtualization related features on Dell Latitude E6500 (BIOS A16), Gentoo ~AMD64 X server with nvidia 185.18.36 or 190.42 goes bad - starting X results in black screen and LCD backlight turns off after ~10 sec. It's not possible to kill X/restore system, still SSH works fine.
dmesg is filled with messages:
DRHD: handling fault status reg 2
DMAR:[DMA Read] Request device [01:00.0] fault addr 113072000
DMAR:[fault reason 01] Present bit in root entry is clear

Disabling anything virtualization (VT-d) related fixes issue, still it would be nice to be able to use virtualization AND nvidia drivers at same time.