![]() ![]() In case you would like to use a CPU feature that is not integrated within the OpenNebula interfaces, e.In the previous post we managed to try our simplistic EFI loader on 64-bit ARM (See the below image for more information) The CPU features are also fully integrated and can be easily enabled in sunstone under OS & CPU > Features section in the VM template. If you find out that you need to incorporate some security or performance feature to the CPU model you are using for your VMs, you can always add them by using the RAW section inside the VM template and leaving the field CPU_MODEL empty. We can see here that the CPU of this example is actually vulnerable to spec_store_bypass.Īnother interesting way of examining the guest OS in search of CPU vulnerabilities is by running some Spectre checkers like. Spectre_v2:Mitigation: Full generic retpoline, STIBP: disabled, RSB filling Spectre_v1:Mitigation: usercopy/swapgs barriers and _user pointer sanitization Mds:Vulnerable: Clear CPU buffers attempted, no microcode SMT Host state unknown For example, let’s check the content of /sys/devices/system/cpu/vulnerabilities $ cd /sys/devices/system/cpu/vulnerabilities Here you can find out which features are exposed by each QEMU CPU model.Īt this point, it is also quite sensible to check which security mitigations are enabled and which are left vulnerable inside the guest OS. Once you have selected a base QEMU CPU model, you need to check if it satisfies your restrictions. Application Development Guide: Capability information.Driver capabilities XML format: Host capabilities.More info about how to obtain information about the capabilities of the virtualization host via the libvirt toolkit can be found here: According to the official documentation, the best QEMU model we’d have to choose in order to fit the specs of this heterogeneous datacenter would be Haswell-IBRS. This way you’ll make sure you are using the optimum model compatible with all of them while -and this is important -preserving the ability to live migrate VMs.įor example, imagine you have these three different CPU models: Skylake-Client-IBRS, Broadwell-noTSX-IBRS and Haswell-IBRS. Once you have your server specs, follow QEMU docs to select the best QEMU model supported by all your hosts. In that case, just repeat the process described above to find out which QEMU CPU models fits your hardware specs. However, this might not always be an option. You may want to group servers by CPU model in different OpenNebula clusters and then use the virtual CPU model closest to the hypervisor model. Note that the CPU model is r etrieved automatically during the host monitoring process and stored in KVM_CPU_MODEL □ If all your hosts have the same CPU, you can use this CPU model straightaway. You can see below the output when executed on a laptop: īy checking /host/cpu/model we can get the closest QEMU CPU model that fits the hardware of our host, in this case Broadwell-noTSX-IBRS. To do so, we can use the virsh -c qemu:///system capabilities command. The first step is always to find the closest QEMU CPU model that fits our hardware. In this post, I’d like to share my approach for selecting a CPU model for KVM x86 hosts, and some tips on how to deal with the possible restrictions you might face during that process. There are many factors that can limit our options, like security or performance restrictions, or even the hardware you are using in your data center. Sometimes it can be hard to choose a CPU model for VMs. ![]()
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