KB2712156–AVX Does Not Work In AM On W2008 R2Host With AMD CPU That Is AVX Capable

Microsoft released a hotfix to deal with an issue where AVX instructions do not work in a virtual machine on a Windows Server 2008 R2-based computer that has an AMD CPU which supports the AVX feature.

Consider the following scenario:

  • An AMD CPU that supports the Advanced Vector Extensions (AVX) feature is installed in a computer that is running Windows Server 2008 R2.
    Note AMD introduces support for the AVX feature in Bulldozer-based multicore processors.
  • You install the Hyper-V server role on the computer.
  • You create a virtual machine on the computer, and then you start the virtual machine.

In this scenario, AVX instructions do not work as expected on the virtual machine.  This issue occurs because the CPUID maximum function limit is not updated to reflect the support for the AVX feature on AMD processors.

A supported hotfix is available from Microsoft.

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