Why can not get the expected cpu topology after setting the maxcpu in xml?

Hello all, I hit a issue that I'm not able to see the expected cpu topology in VM after setting the maxcpu arrtribute in domain. the xml look like below: <vcpu placement='static' current='4'>8</vcpu> <cpu mode='host-passthrough' check='none' migratable='on'> <topology sockets='2' dies='1' cores='4' threads='1'/> </cpu> I notice that the cpu topoloy looked like below capture output from 'lscpu' tool which is totally different with my setting. CPU(s): 4 On-line CPU(s) list: 0-3 Thread(s) per core: 1 Core(s) per socket: 4 Socket(s): 1 NUMA node(s): 1 Vendor ID: GenuineIntel CPU family: 6 Model: 63 Model name: Intel(R) Xeon(R) CPU E5-2699 v3 @ 2.30GHz Besides i found it looked correct if i relpace 'vcpu' line with "<vcpu placement='static'>8</vcpu>" that remove maxcpu value. Could you give me some information? Any comments are appreciated. Thanks