Hi all I have a very weird case of pci passthrough. I have a machine with 7 network interfaces, all of them intel. Four of them are on one quad giga ethernet device. If I manually unbind the devices and allow qemu to use them, with intel IOMMU working, everything works like a charm. Here's how I do it manually: root@kybrat (x86_64) ~]$ lspci -nn | grep net 00:19.0 Ethernet controller [0200]: Intel Corporation 82579V Gigabit Network Connection [8086:1503] (rev 06) 02:00.0 Ethernet controller [0200]: Intel Corporation 82572EI Gigabit Ethernet Controller (Copper) [8086:107d] (rev 06) 05:00.0 Ethernet controller [0200]: Intel Corporation 82571EB Gigabit Ethernet Controller [8086:10a4] (rev 06) 05:00.1 Ethernet controller [0200]: Intel Corporation 82571EB Gigabit Ethernet Controller [8086:10a4] (rev 06) 06:00.0 Ethernet controller [0200]: Intel Corporation 82571EB Gigabit Ethernet Controller [8086:10a4] (rev 06) 06:00.1 Ethernet controller [0200]: Intel Corporation 82571EB Gigabit Ethernet Controller [8086:10a4] (rev 06) 0c:00.0 Ethernet controller [0200]: Intel Corporation 82572EI Gigabit Ethernet Controller (Copper) [8086:107d] (rev 06) echo "8086 10a4" > /sys/bus/pci/drivers/pci-stub/new_id echo "8086 107d" > /sys/bus/pci/drivers/pci-stub/new_id echo "0000:05:00.0" > /sys/bus/pci/devices/0000\:05\:00.0/driver/unbind echo "0000:05:00.0" > /sys/bus/pci/drivers/pci-stub/bind echo "0000:05:00.1" > /sys/bus/pci/devices/0000\:05\:00.1/driver/unbind echo "0000:05:00.1" > /sys/bus/pci/drivers/pci-stub/bind echo "0000:06:00.0" > /sys/bus/pci/devices/0000\:06\:00.0/driver/unbind echo "0000:06:00.0" > /sys/bus/pci/drivers/pci-stub/bind echo "0000:06:00.1" > /sys/bus/pci/devices/0000\:06\:00.1/driver/unbind echo "0000:06:00.1" > /sys/bus/pci/drivers/pci-stub/bind echo "0000:0c:00.0" > /sys/bus/pci/devices/0000\:0c\:00.0/driver/unbind echo "0000:0c:00.0" > /sys/bus/pci/drivers/pci-stub/bind qemu-system-i386 -enable-kvm \ -m 2048 \ -cpu host \ -machine pc-q35-1.6 \ -drive file=/media/virtual/krym.qcow2,if=virtio \ -net none \ -device pci-assign,host=06:00.1,rombar=0 \ -device pci-assign,host=05:00.0,rombar=0 \ -device pci-assign,host=06:00.0,rombar=0 \ -device pci-assign,host=05:00.1,rombar=0 \ -device pci-assign,host=0c:00.0,rombar=0 \ -cdrom /media/virtual/asg-9.107-33.1.iso \ -boot c \ -vnc :0 \ -runas virtual \ -monitor unix:/media/virtual/control/krym/monitor,server,nowait \ -rtc base=localtime,clock=host,driftfix=none This starts qemu and pci passthrough works nicely. Now, if I try to do the same thing through libvirt, virt-install doesn't like the quad ethernet device pci passthrough and I get the error below: virt-install --name=krym --ram=2048 --vcpus=1 --cpu=host --import --os-type=linux --disk path=/media/virtual/krym.qcow2,format=qcow2,bus=virtio --nonetworks --graphics vnc,port=5900 --virt-type=kvm --machine=q35 --accelerate --host-device=pci_0000_06_00_1 --host-device=pci_0000_05_00_0 --host-device=pci_0000_06_00_0 --host-device=pci_0000_05_00_1 --host-device=pci_0000_0c_00_0 Starting install... ERROR Requested operation is not valid: PCI device 0000:06:00.1 is not assignable Domain installation does not appear to have been successful. If it was, you can restart your domain by running: virsh --connect qemu:///system start krym otherwise, please restart your installation. If I try to use just one NIC (any NIC, as long as it's not the quad NIC), things do work: virt-install --name=krym --ram=2048 --vcpus=1 --cpu=host --import --os-type=linux --disk path=/media/virtual/krym.qcow2,format=qcow2,bus=virtio --nonetworks --graphics vnc,port=5900 --virt-type=kvm --machine=q35 --accelerate --host-device=pci_0000_0c_00_0 Starting install... Creating domain... | 0 B 00:00:01 Cannot open display: Run 'virt-viewer --help' to see a full list of available command line options Domain creation completed. You can restart your domain by running: virsh --connect qemu:///system start krym So I guess libvirt has some problem with the intel quad NIC. I will appreciate any help. Thanks, IvanK.