I traced the qemu process, and find out that host cpuid doesn't support x2apic, but VM interception seems enabled x2apic.
with function=1(bit 21 indicates x2apic) host_cpuid:ecx=0x009ce3bd guest_cpuid:ecx=0x00b82201 On 2013-07-22 19:24, Peter Huang(Peng) wrote: > Hi, Everyone > > I have been encountered a problem recently. > My box uses Nehalem E5520 CPU, and this model doesn't support x2apic feature. > I created a VM on KVM, and uses cpu mode=pass-through, I can get the right cpu > model from the VM, but I can also see that the CPU in the vm supports x2apic. > > This seems werid. > From QEMU's CPU model definition, Nehalem also doesn't support x2apic. > > Can anyone explain it? > > Thanks to you all! > > Below is the cpuinfo from host and guest: > host: > fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 > clflush > dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc > arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni > dtes64 > monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 > popcnt lahf_lm dtherm tpr_shadow vnmi flexpriority ept vpid > > vm: > fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 > clflush > mmx fxsr sse sse2 ss ht syscall nx rdtscp lm constant_tsc arch_perfmon > rep_good > nopl pni ssse3 cx16 sse4_1 sse4_2 *x2apic *popcnt hypervisor lahf_lm
