Why does the interface drop out of the bridge?

Question

Virtualization

"Hello, Gentoo, New Year" :)
So.

# uname -a
Linux xxx.xxx.xxx 4.4.17-calculate #1 SMP PREEMPT Tue Aug 16 10:35:59 UTC 2016 x86_64 Intel(R) Core(TM) i5-2300 CPU @ 2.80GHz GenuineIntel GNU/Linux

qemu 2.7.0-r4, libvirt 1.3.5-r2, virt-manager 1.3.2.
Created a virtual Windows Win7. Firewood virtual network card virtio, everything is installed, everything works.
The br0 bridge is created and when Windows is turned on, its vnet0 interface is added to it
BUT. If you leave Windows in the background so that it hangs for a long time without doing anything - for example, at night - in the morning there will be a message from virt-manager that it cannot connect to QEMU and there is no vnet0 interface in the br0 bridge .
You do
# brctl addif br0 vnet0
and everything takes off again. The question is why the interface falls out of the bridge and how to make sure that it does not fall out?

Answer 1

Try disabling power saving on Win7, paravirtual drivers are now so good that they allow Windows to go to sleep, and the hypervisor understands this and puts the VM into a pause state. Maybe that's why the interface falls off.