CONFIG_DMAR and CONFIG_INTR_REMAP for KVM PCI Pass through

[Andrew Mason]

Hello All,
I was attempting to restore a previously working (with Karmic) KVM guest
which had a PCI device passed through to it and noticed that the
64-server kernel has the following config. 

>From /boot/config-2.6.32-21-server:

# CONFIG_DMAR is not set
# CONFIG_INTR_REMAP is not set


It is my understanding that both this options are required in order for
PCI passthrough to work with VTd capable KVM hosts. 

http://www.linux-kvm.org/page/How_to_assign_devices_with_VT-d_in_KVM

Is my understanding correct? If so was this option specifically not set
or is it just that it hadn't been turned on since migrating to the new
kernel ? 


Thanks in advance
Andrew