![]() ![]() Here’s is what we ended up with for our installation.Run the beneath command from the console. I would like to benchmark this, but as of right now I don’t have a good way to do that. Which means disabling TSX could make the VM’s slower. According to different benchmarks, TSX/TSX-NI can provide aroundĤ0% faster applications execution in specific workloads, and 4–5 times more database ISA) that adds hardware transactional memory support, speeding up execution of multi-threaded Transactional Synchronization Extensions (TSX), also called Transactional SynchronizationĮxtensions New Instructions (TSX-NI), is an extension to the x86 instruction set architecture ( noTSX in the CPU modelįor some reason the VM refused to get further than the Windows logo when noTSX wasn’t provided in models past Broadwell.Ī quick search revealed the following from Wikipedia Local APIC that is, each virtual processor has a local APIC instance with the SynIC extensions.īut also, interestingly a page about all the possible tags you can put into a qemu-kvm xml file: The use of a synthetic interrupt controller (SynIC) which is an extension of a virtualized The hypervisor virtualizes interrupt delivery to virtual processors. Looking into this gave me some useful information about why this tag could be important.įrom the Microsoft Hyper-V documentation: It turned out that there were in this case two things that really mattered: 1. With a working Hyper-V VM up and running, I could start trying to remove tag by tag to see which tags were actually required, and because of my curiosity, I looked a bit deeper into these tags. Skylake-Server-noTSX-IBRS Finding out which tags were actually required This is the first configuration where the server didn’t freeze after just a few minutes: And while doing this search I came across something that others had set as a type of tag in their CPU model: Skylake-Server-noTSX-IBRS. We made sure the newest virtio drivers were installed and then googled more about what tags we could use to get the VM to behave.Īnd there were many suggestions, and my first attempt was basically to use them all to see if anything worked. More searches on the internet revealed that this could come from a few different places, but usually related to either the, the or the tags in the machine configuration file, or the virtio drivers in the VM. The error message being SYNTHETIC WATCHDOG TIMEOUT So, we copied the settings that had worked on the first installation, expecting that to work on the next one as well.īut that server was of a slightly different CPU model Skylake-Server-IBRS (Intel(R) Xeon(R) Gold 6126 CPU 2.60GHz) and that was enough to make more trouble.īecause now we got freezes and sometimes BSOD about 2 minutes after booting the Hyper-V server. Now that we had one Hyper-V server running nested virtualization inside of kvm, we needed another one for a different purpose on a different hypervisor (cluster). So, the first server got set up with a virtually downgraded CPU, but seemed to be functional. The loading indicator wheel didn’t even show. Which was quite annoying, considering the fact that it was a Skylake-Server-IBRS (Intel(R) Xeon(R) Silver 4114 CPU 2.20GHz) CPU in the server.īut when we tried something higher than Broadwell, it just didn’t get farther than the windows logo. ![]() ![]() Turns out we hadn’t enabled the VMX tag for the CPU in the libvirt VM configuration file: How-to enable nested virtualization from Enabling Hyper-V on the Windows Guest - or where the trouble startedĪfter a windows guest was installed on the hypervisor, we enabled the Hyper-V feature. The following link gives instructions for Turning on nested virtualization is fairly straight forward. ![]() But running Hyper-V on bare-metal would in this case take up more resources than reasonable for us, so we’re nesting it inside one of our kvm clusters.īut getting Hyper-V 2019 to actually run steadily using nested virtualization inside of qemu-kvm provided some challenges that turned into a long session of trial and error, finding out which tags and features were necessary to get Windows to behave for more than 2 minutes without crashing. We have a few projects coming up where we for different and exciting reasons need to use Hyper-V. TLDR: Jump to the end for the XML tags we found necessary to get this working. ![]()
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