KVM Forum 2019

Many common workloads aren't sensitive to the VM-Exit performance or they can be optimized through device assignment. The focus of this presentation will be on those workloads that are sensitive to the VM-Exit performance and that cannot avoid triggering high frequency VM-Exits. Those workloads aren't common, but they can materialize in the guest with some applications like databases. Incidentally those are also the workloads that show the biggest impact from the software mitigations of some CPU model speculative execution vulnerabilities.

The KVM x86-64 VM-Exits are already highly optimized, but there is still room for improvement. We'll first analyze the impact of various software mitigations on the VM-Exit execution and then how we can change KVM in order to Micro-Optimize the VM-Exit further, with, but also without, the software mitigations enabled.