Intel Westmere missing feature pclmulqdq(pclmuldq) in vm guests

Solution Verified - Updated -


  • In a virtual guest running on a Westmere cpu when using the cpu feature pclmulqdq (also called pclmuldq), performance is lower compared to a physical host

  • Checking the /proc/cpu flags for pclmulqdq(or pclmuldq) support, it is missing on the virtual machine, it will be present on the physical host if on a Westmere cpu.


  • Red Hat Enterprise Virtualization (RHEV) based on RHEL6 hypervisors

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