-cpu haswell / broadwell have no MONITOR in features1 In qemu 2.9.0 if you run qemu-system-x86_64 -cpu Broadwell (or Haswell) then the CPU features1 flag include the SSE3 bit, but do NOT include the MONITOR/MWAIT bit. This is so even when the host includes the features. Additionally, running qemu in this manner results in several error messages: warning: TCG doesn't support requested feature: CPUID.01H:ECX.fma [bit 12] warning: TCG doesn't support requested feature: CPUID.01H:ECX.pcid [bit 17] warning: TCG doesn't support requested feature: CPUID.01H:ECX.x2apic [bit 21] warning: TCG doesn't support requested feature: CPUID.01H:ECX.tsc-deadline [bit 24] warning: TCG doesn't support requested feature: CPUID.01H:ECX.avx [bit 28] warning: TCG doesn't support requested feature: CPUID.01H:ECX.f16c [bit 29] warning: TCG doesn't support requested feature: CPUID.01H:ECX.rdrand [bit 30] warning: TCG doesn't support requested feature: CPUID.07H:EBX.hle [bit 4] warning: TCG doesn't support requested feature: CPUID.07H:EBX.avx2 [bit 5] warning: TCG doesn't support requested feature: CPUID.07H:EBX.invpcid [bit 10] warning: TCG doesn't support requested feature: CPUID.07H:EBX.rtm [bit 11] warning: TCG doesn't support requested feature: CPUID.07H:EBX.rdseed [bit 18] warning: TCG doesn't support requested feature: CPUID.80000001H:ECX.3dnowprefetch (Among possible other uses, the lack of the MONITOR feature bit causes NetBSD to fall-back on a check-and-pause loop while an application CPU is waiting to be told to proceed by the boot CPU.)