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Add PCI Troubleshooting

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PROTechThor 2020-10-18 10:08:03 +01:00
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user/common-tasks/pci-devices.md
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@ -81,30 +81,7 @@ For example, if `00_1a.0` is the BDF of the device you want to attach to the "wo
## Possible Issues ##
### DMA Buffer Size ###
VMs with attached 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=8192"
This is [known to be needed][ml1] for the Realtek RTL8111DL Gigabit Ethernet Controller.
### PCI Passthrough Issues ###
Sometimes the PCI arbitrator is too strict.
There is a way to enable permissive mode for it.
See also: [this thread][ml2] and the Xen wiki's [PCI passthrough] page.
At other times, you may instead need to disable the FLR requirement on a device.
Both can be achieved during attachment with `qvm-pci` as described below.
Visit the [PCI Troubleshooting guide](pci-troubleshoot) to see issues that may arise due to PCI devices and how to troubleshoot them.
## Additional Attach Options ##
@ -166,9 +143,7 @@ or
[USB]:/doc/usb-devices/
[appmenu]: /attachment/wiki/Devices/qubes-appmenu-select.png
[domain manager icon]: /attachment/wiki/Devices/qubes-logo-icon.png
[pci-troubleshoot]:/doc/pci-troubleshooting
[qvm-device]: /doc/device-handling/#general-qubes-device-widget-behavior-and-handling
[side channel attacks]: https://en.wikipedia.org/wiki/Side-channel_attack
[ml1]: https://groups.google.com/group/qubes-devel/browse_thread/thread/631c4a3a9d1186e3
[ml2]: https://groups.google.com/forum/#!topic/qubes-users/Fs94QAc3vQI
[PCI passthrough]: https://wiki.xen.org/wiki/Xen_PCI_Passthrough