Windows DomU: Network Issues

[Paul Leiber <paul@xxxxxxxxxxxxxxxx>]

Hi everybody,

I am a novice Xen user. I recently started to set up my home server (file 
server, print server, media server, TV backend etc.) using Xen based VMs 
installed on a Debian 10 dom0. I mostly followed the steps laid out in 
https://wiki.xenproject.org/wiki/Xen_Project_Beginners_Guide. The linux domUs 
worked like a charm right from the beginning.

I then wanted to install Windows Server 2012 on a domU for the TV backend 
(MediaPortal). Following the steps in the above mentioned guide, I could 
install the Windows system alright. I could solve most of the obvious issues 
(like mouse pointer off, keyboard layout not correct etc.). However, I utterly 
failed to get a decent network connection. Transfer speed while copying a large 
file from a Samba file server on one of the Debian domUs to the Windows Server 
2012 domU remained around 1-3 Mbit/s. I of course installed the Windows PV 
drivers from https://xenproject.org/windows-pv-drivers/, tried different 
options in the config file, added the GplPv option to the boot options (as 
described in https://wiki.xenproject.org/wiki/Xen_Windows_GplPv/Installing), 
but nothing helped. The slow connection made it pointless to use the Windows 
Server DomU as a media/TV server. Also, there was a persistent error on Windows 
Update so I couldn't install any updates. I tried a fresh install, but with the 
same result. I gave up and installed VDR on another Debian DomU which works o.k.

But now it turns out my wife is not happy with the Kodi frontend, so I am 
forced to give Windows another try. This time, I installed Windows 10, but the 
results are the same (except for the Windows Update, which now works). Now I am 
lost. Any help for pinpointing the error and/or finding a solution (besides the 
obvious one, to replace my wife ;-) would be very much appreciated. Or is this 
in the end the maximum network speed to be expected on a HVM domU like Windows?

Further observations from Windows 10 device manager on the domU:
- There is one device without a driver (yellow triangle), the device is called 
XSC000 XENVIF 0
- The system devices XenServer PV Interface, XenServer PV Bus (twice), and 
XenServer PV Network Class seem to be installed correctly
- The NIC installed is shown as Realtek RTL8139C+ Fast Ethernet NIC

Xen config file for the Windows domU:

kernel = "/usr/lib/xen-4.0/boot/hvmloader"
type='hvm'
memory = 4096
vcpus=4
name = "windows"
vif = ['bridge=xenbr0']
disk = ['phy:/dev/vg0/windows,hda,w']
device_model_version = 'qemu-xen'
boot="c"
hdtype = 'ahci'
acpi = 1
apic = 1
xen_platform_pci = 1
vendor_device = 'xenserver'
stdvga = 1
device_model_version = 'qemu-xen'
boot = "d"
sdl = 0
pae = 1
serial = 'pty'
usb = 1
usbdevice = 'tablet'
keymap = 'de'
vnc = 1
vnclisten = "0.0.0.0"
vncpasswd = ""

xl info:

host                   : xxx
release                : 4.19.0-14-amd64
version                : #1 SMP Debian 4.19.171-2 (2021-01-30)
machine                : x86_64
nr_cpus                : 4
max_cpu_id             : 3
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 1992.095
hw_caps                : 
bfebfbff:77faf3ff:2c100800:00000121:0000000f:009c6fbf:00000000:00000100
virt_caps              : hvm hvm_directio
total_memory           : 32542
free_memory            : 18773
sharing_freed_memory   : 0
sharing_used_memory    : 0
outstanding_claims     : 0
free_cpus              : 0
xen_major              : 4
xen_minor              : 11
xen_extra              : .4
xen_version            : 4.11.4
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 
hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          :
xen_commandline        : placeholder dom0_mem=1024M,max:1024M 
xen-pciback.hide=(01:00.0)
cc_compiler            : gcc (Debian 8.3.0-6) 8.3.0
cc_compile_by          : pkg-xen-devel
cc_compile_domain      : lists.alioth.debian.org
cc_compile_date        : Fri Dec 11 21:33:51 UTC 2020
build_id               : 6d8e0fa3ddb825695eb6c6832631b4fa2331fe41
xend_config_format     : 4

Logs from /var/log/xen didn't show errors, but can of course be provided if 
needed.

Best regards,

Paul