I was able to avoid rebooting after following @Andrii's instructions - https://bugs.launchpad.net/qemu/+bug/1703506/comments/19 - above:
systemctl stop libvirtd libvirtd-admin.socket libvirtd-ro.socket libvirtd.socket sudo modprobe -r kvm_intel kvm systemctl start libvirtd libvirtd-admin.socket libvirtd-ro.socket libvirtd.socket These instructions to avoid rebooting might not work for those using a non-Intel CPU as you'll have a different kernel module. You can check by running `lsmod | grep kvm`. Cheers, ak. System info: # inxi -CMz Machine: Type: Laptop System: Dell product: Precision M6700 v: 01 serial: <filter> Mobo: Dell model: 0JWMFY v: A00 serial: <filter> UEFI: Dell v: A20 date: 11/30/2018 CPU: Info: quad core model: Intel Core i7-3840QM bits: 64 type: MT MCP cache: L2: 1024 KiB Speed (MHz): avg: 3607 min/max: 1200/3800 cores: 1: 3588 2: 3615 3: 3638 4: 3588 5: 3588 6: 3638 7: 3617 8: 3588 -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1703506 Title: SMT not supported by QEMU on AMD Ryzen CPU Status in QEMU: Expired Bug description: HyperThreading/SMT is supported by AMD Ryzen CPUs but results in this message when setting the topology to threads=2: qemu-system-x86_64: AMD CPU doesn't support hyperthreading. Please configure -smp options properly. Checking in a Windows 10 guest reveals that SMT is not enabled, and from what I understand, QEMU converts the topology from threads to cores internally on AMD CPUs. This appears to cause performance problems in the guest perhaps because programs are assuming that these threads are actual cores. Software: Linux 4.12, qemu 2.9.0 host with KVM enabled, Windows 10 pro guest To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1703506/+subscriptions