The warning doesn't make QEMU disable anything, it just warns the user that guests are likely to ignore the HT info on CPUID if CPU vendor is AMD.
Please confirm what's the QEMU command-line being used (especially the -smp and -cpu options), and check if the bug persists if using "-cpu host". To help find out what's wrong, I'd like to see /proc/cpuinfo, "lscpu -e" output and "x86info -v -a" output from both the host system and the guest system. -- 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: New 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