VMExits caused by guest accesses to IPIs and timers have been observed as two of major overheads in virtualization. Lots of efforts have been taken in the community to reduce them. Most of them are designed for the public cloud scenarios and must follow the assertion that everything in VMs is untrusted. However, such assertion can be loosen in the private cloud scenarios where VMs can be partially trusted. Therefore, more aggressive optimization can be applied. In this talk, we will introduce our optimizations on guest IPIs and timers for KVM VMs in a private cloud. The optimizations are composed of an aggressive PV IPIs and a passthrough timer, which can eliminate most VMExits on both the setup and the interrupt injection paths. According to our early evaluation in a production environment, above optimizations can bring near bare-metal performance for certain guest workloads.
