Hi!

Using Qubes-R3.0-rc1-x86_64-DVD.iso and a notebook with a RTL8191SEvB.

kernel: Qubes, with Xen 4.4.2 and Linux 3.12.40-1.pvops.qubes.x86_64

(Not using newer kernel due to unrelated graphic issues that are to be
sorted out later.)

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How?

1) System Tools -> Konsole (Terminal)

2) qvm-prefs -s sys-net kernelopts "nopat iommu=soft swiotlb=8192"

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Trivia:

- Left sys-net Qubes VM 300MB initial memory setting as is.

- Fedora-Live-Workstation-x86_64-22-3.iso works out of the box.

- On Debian wheezy I needed to install the
https://packages.debian.org/wheezy/firmware-realtek package.

References:

- https://www.qubes-os.org/doc/AssigningDevices/

- https://groups.google.com/forum/#!topic/qubes-devel/YxxKOp0RhuM

Cheers,
Patrick