12.profile cannot use with virtual machine

[Tigerlee233]

In the 'main' function of profile.c,I cannot define the attr.type to PERF_TYPE_HARDWARE because the virtualmachine has no entry to the performance count. After changed the code like these:
attr.type = PERF_TYPE_HARDWARE;
attr.size = sizeof(attr);
attr.config = PERF_COUNT_HW_CPU_CYCLES;
I can run the profile in my virtual machine. I would like to confirm if my views are correct.And could you tell me the differeces of these two type: PERF_TYPE_HARDWARE & PERF_TYPE_SOFTWARE? If I get the online cpus' information of kernel stacks and user stacks,what's the difference between I get these information from HARD or SOFT?