A Hypervisor Approach to Enable Live Migration with Passthrough SR-IOV Network Devices

Single-Root I/O Virtualization (SR-IOV) is a specification that allows a single PCI Express (PCIe) device (physical function or PF) to be used as multiple PCIe devices (virtual functions or VF). In a virtualization system, each VF can be directly assigned to a virtual machine (VM) in passthrough mode to significantly improve the network performance. However, VF passthrough mode is not compatible with live migration, which is an essential capability that enables many advanced virtualization features such as high availability and resource provisioning. To solve this problem, we design SRVM which provides hypervisor support to ensure the VF device can be correctly used by the migrated VM and the applications. SRVM is implemented in the hypervisor without modification in guest operating systems or guest VM drivers. SRVM does not increase VM downtime. It only costs limited resources (an extra CPU core only during the live migration pre-copy phase), and there is no significant runtime overhead in VM network performance.