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102 lines
3.2 KiB
Markdown
102 lines
3.2 KiB
Markdown
---
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layout: wiki
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title: AssigningDevices
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permalink: /wiki/AssigningDevices/
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---
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Assigning Devices to VMs
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========================
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In order to assign a whole PCI(e) device to a VM, one should use `qvm-pci` tool. E.g.
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``` {.wiki}
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lspci
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```
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Find the BDF address of the device you want to assign, and then:
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``` {.wiki}
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qvm-pci -a <vmname> <bdf>
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```
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E.g. assuming 00:1a.0 is a BDF of the device I want to assign to the "personal" domain:
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``` {.wiki}
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qvm-pci -a personal 00:1a.0
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```
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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.
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Using Qubes Manager
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-------------------
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TODO
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\<screenshot\>
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Finding the right USB controller
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--------------------------------
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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:
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``` {.wiki}
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lsusb
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```
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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):
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``` {.wiki}
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Bus 003 Device 003: ID 413c:818d Dell Computer Corp.
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```
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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:
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``` {.wiki}
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readlink /sys/bus/usb/devices/usb3
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```
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This should output something like:
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``` {.wiki}
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../../../devices/pci-0/pci0000:00/0000:00:1a.0/usb3
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```
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Now you see BDF address in the path (right before final usb3). Strip leading "0000:" and pass the rest to qvm-pci tool:
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``` {.wiki}
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qvm-pci -a netvm 00:1a.0
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```
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Possible issues
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---------------
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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):
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``` {.wiki}
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# qvm-prefs netvm |grep kernelopts
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kernelopts : iommu=soft swiotlb=2048 (default)
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# qvm-prefs -s netvm kernelopts "iommu=soft swiotlb=4096"
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```
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This is [known to be needed](https://groups.google.com/group/qubes-devel/browse_thread/thread/631c4a3a9d1186e3) for Realtek RTL8111DL Gigabit Ethernet Controller.
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Bringing PCI device back to dom0
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--------------------------------
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By default device detached from some VM (or when VM with PCI device attached get shut down) isn't attached back to dom0. This is an intended feature. A device which was previously assigned to a less trusted AppVM could attack dom0 if it were automatically reassigned there. In order to re-enable the device in dom0, either:
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1. Reboot the physical machine.
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or
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1. Go to the sysfs (`/sys/bus/pci`), find the right device, detach it from the pciback driver and attach back to the original driver. Replace `<BDF>` with your device, for example `00:1c.2`:
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``` {.wiki}
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echo 0000:<BDF> > /sys/bus/pci/drivers/pciback/unbind
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MODALIAS=`cat /sys/bus/pci/devices/0000:<BDF>/modalias`
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MOD=`modprobe -R $MODALIAS | head -n 1`
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echo <BDF> > /sys/bus/pci/drivers/$MOD/bind
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```
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