Using CPUID as a serializing instruction before RDTSC{,P} is a bad bad thing to do inside a virtual machine on Intel processors. CPUID will cause a VMEXIT, and

Using CPUID as a serializing instruction before RDTSC{,P} is a bad bad thing to do inside a virtual machine on Intel processors. CPUID will cause a VMEXIT, and the CPUID instruction will be emulated. The Intel Software Development Manual Instruction Set Reference gives good guidance on using MFENCE and LFENCE as required. https://software.intel.com/sites/default/files/managed/39/c5/325462-sdm-vol-1-2abcd-3abcd.pdf#page=1667 https://software.intel.com/sites/default/files/managed/39/c5...