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AssigningDevices changed

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info about swiotlb
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Marek Marczykowski-Górecki 2012-08-06 23:35:05 +00:00
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AssigningDevices.md
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@ -23,3 +23,15 @@ 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.
### Possible issues
VM with PCI device in Qubes have allocated small buffer for DMA operations (called swiotlb). By default it is 2MB, but some devices needs a larger space. To change this allocation, edit VM kernel parameters (this is expressed in 512B chunks):
``` {.wiki}
# qvm-prefs netvm |grep kernelopts
kernelopts : iommu=soft swiotlb=2048 (default)
# qvm-prefs -s netvm kernelopts "iommu=soft swiotlb=4096"
```
This is [​know to be needed](https://groups.google.com/group/qubes-devel/browse_thread/thread/631c4a3a9d1186e3) for Realtek RTL8111DL Gigabit Ethernet Controller.