Hi all, the last year I’ve been running a lot of tests in my OpenShift lab environment, and I was quite curious about how OpenShift Virtualization works.\u00a0\u00a0 OpenShift Virtualization is a feature of Red Hat OpenShift Container Platform (OCP) that allows you to run and manage virtual machines alongside containers in the same OCP Cluster.<\/p>\n
As most of virtualization technologies like VMware, Hyper-V, KVM and others, OpenShift Virtualization requires hardware virtualization, which usually means that you need to use bare-metal servers for your OCP cluster.\u00a0 By default, OpenShift Virtualization uses the Linux Kernel Virtual Machine (KVM), which is a full-virtualization solution for Linux on x86 hardware. KVM uses the virtualization extensions Intel VT or AMD-V to enable device emulation.\u00a0 Of course, in a lab environment isn’t always possible to have physical servers available for this kind of tests, so we usually leverage nested virtualization, like when we want to run a virtual ESXi host on top of a physical ESXi host.<\/p>\n
One of the option we have, is to run our OCP cluster as VMs on top of VMware or KVM, and enable nested virtualization:<\/p>\n
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But what if we are trying to run an OCP cluster in a Cloud provider like AWS EC2, Azure VMs or Google Cloud Engine?\u00a0 In this case the situation is a bit more complicated, as we can’t just expose the Hardware Virtualization extensions, like Intel VT or AMD-V,\u00a0 to enable device emulation<\/p>\n
And well, that’s my case as I don’t have enough resources in my VMware-based homelab to run an OCP cluster, not even mention OCP Virtualization, so I’ve deployed an OpenShift Cluster on Google Cloud using GCE VM instances, which works perfectly fine until I tried to use OpenShift Virtualization of course :)<\/p>\n
In this kind of scenario you need to switch OpenShift Virtualization from its default of hardware virtualization to QEMU-based software emulation<\/strong>.\u00a0 Just then you will be able to run a virtual machine using OpenShift Virtualization, even in a non-bare metal instance such as GCE VM Instance.<\/p>\n In this post I’ll explain how to enable Software Emulation in OpenShift Virtualization, to be able to run VMs when the default Hardware Virtualization isn’t available.<\/p>\n <\/p>\n NOTE<\/strong>: The following workaround is not supported by Red Hat, even for dev\/test\/sandbox environments.\u00a0\u00a0 For performance reasons, hardware virtualization, where the virtual machine uses the hardware directly, is\u00a0 always preferable over software virtualization in real-world implementations. Modern CPUs, memory, and hardware components are designed with hardware virtualization in mind.\u00a0\u00a0 Running VMs through OpenShift Virtualization’s software emulation method can result in performance degradation.<\/p>\n <\/p>\n