mirror of
https://github.com/QubesOS/qubes-doc.git
synced 2024-12-18 04:04:39 -05:00
145 lines
6.8 KiB
Markdown
145 lines
6.8 KiB
Markdown
---
|
|
lang: en
|
|
layout: doc
|
|
permalink: /doc/how-to-use-pci-devices/
|
|
redirect_from:
|
|
- /doc/pci-devices/
|
|
- /doc/assigning-devices/
|
|
- /en/doc/assigning-devices/
|
|
- /doc/AssigningDevices/
|
|
- /wiki/AssigningDevices/
|
|
ref: 197
|
|
title: How to use PCI devices
|
|
---
|
|
|
|
*This page is part of [device handling in qubes](/doc/how-to-use-devices/).*
|
|
|
|
**Warning:** Only dom0 exposes PCI devices.
|
|
Some of them are strictly required in dom0 (e.g., the host bridge).
|
|
You may end up with an unusable system by attaching the wrong PCI device to a VM.
|
|
PCI passthrough should be safe by default, but non-default options may be required.
|
|
Please make sure you carefully read and understand the **[security considerations](/doc/device-handling-security/#pci-security)** before deviating from default behavior.
|
|
|
|
## Introduction
|
|
|
|
Unlike other devices ([USB](/doc/how-to-use-usb-devices/), [block](/doc/how-to-use-block-storage-devices/), mic), PCI devices need to be attached on VM-bootup.
|
|
Similar to how you can't attach a new sound-card after your computer booted (and expect it to work properly), attaching PCI devices to already booted VMs isn't supported.
|
|
Moreover, PCI devices can be attached only to VMs running in certain virtualization modes. See [FAQ: Which virtualization modes do VMs use?](/faq/#which-virtualization-modes-do-vms-use)
|
|
|
|
The Qubes installer attaches all network class controllers to `sys-net` and all USB controllers to `sys-usb` by default, if you chose to create the network and USB qube during install.
|
|
While this covers most use cases, there are some occasions when you may want to manually attach one NIC to `sys-net` and another to a custom NetVM, or have some other type of PCI controller you want to manually attach.
|
|
|
|
Some devices expose multiple functions with distinct BDF-numbers.
|
|
Limits imposed by the PC and VT-d architectures may require all functions belonging to the same device to be attached to the same VM.
|
|
This requirement can be dropped with the `no-strict-reset` option during attachment, bearing in mind the aforementioned [security considerations](/doc/device-handling-security/#pci-security).
|
|
In the steps below, you can tell if this is needed if you see the BDF for the same device listed multiple times with only the number after the "." changing.
|
|
|
|
While PCI device can only be used by one powered on VM at a time, it *is* possible to *assign* the same device to more than one VM at a time.
|
|
This means that you can use the device in one VM, shut that VM down, start up a different VM (to which the same device is now attached), then use the device in that VM.
|
|
This can be useful if, for example, you have only one USB controller, but you have multiple security domains which all require the use of different USB devices.
|
|
|
|
## Attaching Devices Using the GUI
|
|
|
|
The qube settings for a VM offers the "Devices"-tab.
|
|
There you can attach PCI-devices to a qube.
|
|
|
|
1. To reach the settings of any qube either
|
|
|
|
- Press Alt+F3 to open the application finder, type in the VM name, select the "\[VM-name\]: Qube Settings" menu entry and press enter or click "Launch"!
|
|
- Select the VM in Qube Manager and click the settings-button or right-click the VM and select `Qube settings`.
|
|
- Click the Domain Manager, hover the VM you want to attach a device to and select "settings" in the additional menu. (only running VMs!)
|
|
|
|
2. Select the "Devices" tab on the top bar.
|
|
3. Select a device you want to attach to the qube and click the single arrow right! (`>`)
|
|
4. You're done.
|
|
If everything worked out, once the qube boots (or reboots if it's running) it will start with the pci device attached.
|
|
5. In case it doesn't work out, first try disabling memory-balancing in the settings ("Advanced" tab).
|
|
If that doesn't help, read on to learn how to disable the strict reset requirement!
|
|
|
|
## `qvm-pci` Usage
|
|
|
|
The `qvm-pci` tool allows PCI attachment and detachment.
|
|
It's a shortcut for [`qvm-device pci`](/doc/how-to-use-devices/#general-qubes-device-widget-behavior-and-handling).
|
|
|
|
To figure out what device to attach, first list the available PCI devices by running (as user) in dom0:
|
|
|
|
```
|
|
qvm-pci
|
|
```
|
|
|
|
This will show you the `backend:BDF` (Bus_Device.Function) address of each PCI device.
|
|
It will look something like `dom0:00_1a.0`.
|
|
Once you've found the address of the device you want to attach, then attach it like this:
|
|
|
|
```
|
|
qvm-pci attach targetVM sourceVM:[BDF] --persistent
|
|
```
|
|
|
|
Since PCI devices have to be attached on bootup, attaching has to happen with the `--persistant` option.
|
|
|
|
For example, if `00_1a.0` is the BDF of the device you want to attach to the "work" domain, you would do this:
|
|
|
|
```
|
|
qvm-pci attach work dom0:00_1a.0 --persistent
|
|
```
|
|
|
|
## Possible Issues
|
|
|
|
Visit the [PCI Troubleshooting guide](/doc/pci-troubleshooting/) to see issues that may arise due to PCI devices and how to troubleshoot them.
|
|
|
|
## Additional Attach Options
|
|
|
|
Attaching a PCI device through the commandline offers additional options, specifiable via the `--option`/`-o` option.
|
|
(Yes, confusing wording, there's an [issue for that](https://github.com/QubesOS/qubes-issues/issues/4530).)
|
|
|
|
`qvm-pci` exposes two additional options.
|
|
Both are intended to fix device or driver specific issues, but both come with [heavy security implications](/doc/device-handling-security/#pci-security)! **Make sure you understand them before continuing!**
|
|
|
|
### no-strict-reset
|
|
|
|
Do not require PCI device to be reset before attaching it to another VM.
|
|
This may leak usage data even without malicious intent!
|
|
|
|
usage example:
|
|
|
|
```
|
|
qvm-pci a work dom0:00_1a.0 --persistent -o no-strict-reset=true
|
|
```
|
|
|
|
### permissive
|
|
|
|
Allow write access to full PCI config space instead of whitelisted registers.
|
|
This increases attack surface and possibility of [side channel attacks](https://en.wikipedia.org/wiki/Side-channel_attack).
|
|
|
|
usage example:
|
|
|
|
```
|
|
qvm-pci a work dom0:00_1a.0 --persistent -o permissive=true
|
|
```
|
|
|
|
## Bringing PCI Devices Back to dom0
|
|
|
|
By default, when a device is detached from a VM (or when a VM with an attached PCI device is shut down), the device is *not* automatically attached back to dom0.
|
|
|
|
This is an intended feature.
|
|
|
|
A device which was previously attached to a VM less trusted than dom0 (which, in Qubes, is *all* of them) could attack dom0 if it were automatically reattached there.
|
|
|
|
In order to re-enable the device in dom0, either:
|
|
|
|
- Reboot the physical machine. (Best practice)
|
|
|
|
or
|
|
|
|
- Go to the sysfs (`/sys/bus/pci`), find the right device, detach it from the pciback driver, and attach it back to the original driver.
|
|
Replace `<BDF>` with your full device, for example `0000:00:1c.2`:
|
|
|
|
```
|
|
echo <BDF> > /sys/bus/pci/drivers/pciback/unbind
|
|
MODALIAS=`cat /sys/bus/pci/devices/<BDF>/modalias`
|
|
MOD=`modprobe -R $MODALIAS | head -n 1`
|
|
echo <BDF> > /sys/bus/pci/drivers/$MOD/bind
|
|
```
|
|
|
|
It is **strongly discouraged to reattach PCI devices to dom0**, especially if they don't support resetting!
|