The core topology info used by Linux (see linux/arch/x86/kernel/cpu/amd.c:amd_get_topology()) is actually at CPUID[0x8000001e].
AMD's documentation is a bit confusing, as the Architecture Programmer's Manual still refers to CPUID[0x8000001e].EBX[bits 7:0] as "compute unit ID", but the Processor Programming Reference for AMD Family 17h documents the same bits as "Core ID". We can implement CPUID[0x8000001e] and print the existing warning only if CPU vendor is AMD and cpuid_family != 0x17. -- 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
