[Windows] Provide workaround to install Hyper-V without CPU check (an…

…trea-io#1744)

Provide workaround to install Hyper-V without CPU virtualization
capability check. In this way, users could deploy antrea on the
node without virtualization capability.

Signed-off-by: Rui Cao <[email protected]>

docs/windows.md

@@ -45,7 +45,9 @@ and daemons are pre-installed on the Windows Nodes in the demo.
   updates.
 * Deploy a Linux-based Kubernetes cluster.
 * Install [Hyper-V](https://docs.microsoft.com/en-us/windows-server/virtualization/hyper-v/get-started/install-the-hyper-v-role-on-windows-server)
-  with management tools.
+  with management tools. If your Nodes do not have the virtualization
+  capabilities required by Hyper-V, you could try the workaround
+  described in the [Known issues](#Known-issues) section.
 * Install [Docker](https://docs.microsoft.com/en-us/virtualization/windowscontainers/quick-start/set-up-environment?tabs=Windows-Server).
 * [Install OVS](http://docs.openvswitch.org/en/latest/intro/install/windows/)
   and configure the daemons as Windows service.
@@ -328,3 +330,47 @@ the HNS Network created by antrea-agent is removed, and the Open vSwitch
 Extension is disabled by default. In this case, the stale OVS bridge and ports
 should be removed. A help script [Clean-AntreaNetwork.ps1](https://raw.githubusercontent.com/vmware-tanzu/antrea/master/hack/windows/Clean-AntreaNetwork.ps1)
 can be used to clean the OVS bridge.
+
+2. Hyper-V feature cannot be installed on Windows Node due to the processor not
+having the required virtualization capabilities.
+
+    If the processor of the Windows Node does not have the required
+    virtualization capabilities. The installation of Hyper-V feature will fail
+    with the following error:
+
+    ```powershell
+    PS C:\Users\Administrator> Install-WindowsFeature Hyper-V
+
+    Success Restart Needed Exit Code      Feature Result
+    ------- -------------- ---------      --------------
+    False   Maybe          Failed         {}
+    Install-WindowsFeature : A prerequisite check for the Hyper-V feature failed.
+    1. Hyper-V cannot be installed: The processor does not have required virtualization capabilities.
+    At line:1 char:1
+    + Install-WindowsFeature hyper-v
+    + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+        + CategoryInfo          : InvalidOperation: (Hyper-V:ServerComponentWrapper) [Install-WindowsFeature], Exception
+        + FullyQualifiedErrorId : Alteration_PrerequisiteCheck_Failed,Microsoft.Windows.ServerManager.Commands.AddWindowsF
+       eatureCommand
+    ```
+
+    The capabilities are required by the Hyper-V `hypervisor` components to
+    support [Hyper-V isolation](https://docs.microsoft.com/en-us/virtualization/windowscontainers/manage-containers/hyperv-container#hyper-v-isolation).
+    If you only need [Process Isolation](https://docs.microsoft.com/en-us/virtualization/windowscontainers/manage-containers/hyperv-container#process-isolation)
+    on the Nodes. You could apply the following workaround to skip CPU check for
+    Hyper-V feature installation.
+
+    ```powershell
+    # 1. Install containers feature
+    Install-WindowsFeature containers
+
+    # 2. Install Hyper-V management powershell module
+    Install-WindowsFeature Hyper-V-Powershell
+
+    # 3. Install Hyper-V feature without CPU check and disable the "hypervisor"
+    dism /online /enable-feature /featurename:Microsoft-Hyper-V /all /NoRestart
+    dism /online /disable-feature /featurename:Microsoft-Hyper-V-Online /NoRestart
+
+    # 4. Restart-Computer to take effect
+    Restart-Computer
+    ```