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| layout | title | permalink |
|---|---|---|
| wiki | AssigningDevices | /wiki/AssigningDevices/ |
Assigning Devices to VMs
In order to assign a whole PCI(e) device to a VM, one should use qvm-pci tool. E.g.
lspci
Find the BDF address of the device you want to assign, and then:
qvm-pci -a <vmname> <bdf>
E.g. assuming 00:1a.0 is a BDF of the device I want to assign to the "personal" domain:
qvm-pci -a personal 00:1a.0
Note that one can only assign full PCI or PCI Express devices. This means one cannot assign single USB devices -- only the whole USB controller with whatever USB devices connected to it. This limit is imposed by PC and VT-d architecture.
Using Qubes Manager
TODO
<screenshot>
Finding the right USB controller
If you want assign certain USB device to a VM (by attaching a whole USB controller), you need to figure out which PCI device is the right controller. First check to which USB bus the device is connected:
lsusb
For example I want assign a broadband modem to the netvm. In lsusb output it can be listed as something like this (in this case device isn't fully identified):
Bus 003 Device 003: ID 413c:818d Dell Computer Corp.
The device is connected to the USB bus #3. Then check which other devices are connected to the same bus - all of them will be assigned to the same VM. Now is the time to find right USB controller:
readlink /sys/bus/usb/devices/usb3
This should output something like:
../../../devices/pci-0/pci0000:00/0000:00:1a.0/usb3
Now you see BDF address in the path (right before final usb3). Strip leading "0000:" and pass the rest to qvm-pci tool:
qvm-pci -a netvm 00:1a.0
Possible issues
VMs with assigned PCI devices in Qubes have allocated a small buffer for DMA operations (called swiotlb). By default it is 2MB, but some devices need a larger buffer. To change this allocation, edit VM's kernel parameters (this is expressed in 512B chunks):
# qvm-prefs netvm |grep kernelopts
kernelopts : iommu=soft swiotlb=2048 (default)
# qvm-prefs -s netvm kernelopts "iommu=soft swiotlb=4096"
This is known to be needed for Realtek RTL8111DL Gigabit Ethernet Controller.