> >> No, if a feature cannot be emulated, that means it cannot be enabled > >> unless it matches the host. That's generally not a problem since > >> Intel PT is usually used only with "-cpu host". > >> > > The limitation of LIP in qemu will mask off the Intel PT in KVM guest > > even with "-cpu host". e.g. This bit will be set in SnowRidge HW and > > later. > > I agree that QEMU would have to learn about LIP. Unlike this patch, however, > x86_cpu_filter_features would have to fail if host LIP != guest LIP. That is, > something like > > (ecx_0 & INTEL_PT_IP_LIP)) != > (env->features[INTEL_PT_ECX_0] & INTEL_PT_IP_LIP) > > where "intel-pt-lip" would be a feature in env->features[INTEL_PT_ECX_0].
Got it. Thanks. Luwei Kang > > > How about "-cpu cpu_model, +intel-pt" use case? The current value of > > Intel PT CPUID is a constant. Can we make the ICX CPUID as basic > > inforation(LIP is 0) and using "+intel-pt-lip" to make Intel PT work > > on the CPU which LIP is 1 on the host? As you mentioned before, Intel > > PT cannot be enabled in guest unless it matches the host. > > Yes, this would work. > > Paolo
