Hi,
it seem that windows 2012r2 (and windows 8.1) is buggy, and can crash or have cpu at 100% with virtio-net driver
A hotfix is available here (and it's not pushed by default in windows update)
""0x000000D1" Stop error in Pacer.sys when there's heavy QoS traffic in Windows Server 2012 R2"
https://support.microsoft.com/en-us/kb/3101694
kvm bug report here:
https://github.com/YanVugenfirer/kvm-guest-drivers-windows/issues/77
it seem that windows 2012r2 (and windows 8.1) is buggy, and can crash or have cpu at 100% with virtio-net driver
A hotfix is available here (and it's not pushed by default in windows update)
""0x000000D1" Stop error in Pacer.sys when there's heavy QoS traffic in Windows Server 2012 R2"
https://support.microsoft.com/en-us/kb/3101694
kvm bug report here:
https://github.com/YanVugenfirer/kvm-guest-drivers-windows/issues/77