diff --git a/AssigningDevices.md b/AssigningDevices.md
index ccb2a7fd..f422cba3 100644
--- a/AssigningDevices.md
+++ b/AssigningDevices.md
@@ -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.