Current default behavior of QEMU is to silently disable features that are not supported by the host when a CPU model is requested in the command-line. This means that in addition to risking breaking guest ABI by default, we are silent about it. I would like to enable "enforce" by default, but this can easily break existing production systems because of the way libvirt makes assumptions about CPU models today (this will change in the future, once QEMU provide a proper interface for checking if a CPU model is runnable). But there's no reason we should be silent about it. So, change target-i386 to enable "check" mode by default so at least we have some warning printed to stderr (and hopefully logged somewhere) when QEMU disables a feature that is not supported by the host system. Signed-off-by: Eduardo Habkost <ehabkost(a)redhat.com&gt; --- target-i386/cpu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/target-i386/cpu.c b/target-i386/cpu.c index cfb8aa7..32fee00 100644 --- a/target-i386/cpu.c +++ b/target-i386/cpu.c @@ -3121,7 +3121,7 @@ static Property x86_cpu_properties[] = { DEFINE_PROP_BOOL("hv-relaxed", X86CPU, hyperv_relaxed_timing, false), DEFINE_PROP_BOOL("hv-vapic", X86CPU, hyperv_vapic, false), DEFINE_PROP_BOOL("hv-time", X86CPU, hyperv_time, false), - DEFINE_PROP_BOOL("check", X86CPU, check_cpuid, false), + DEFINE_PROP_BOOL("check", X86CPU, check_cpuid, true), DEFINE_PROP_BOOL("enforce", X86CPU, enforce_cpuid, false), DEFINE_PROP_BOOL("kvm", X86CPU, expose_kvm, true), DEFINE_PROP_UINT32("level", X86CPU, env.cpuid_level, 0),