Stefano Stabellini is a Senior Software Engineer at Citrix, working on the Open Source Xen Platform team. He has been working on Xen since 2007, focusing on several different projects, spanning from Qemu to the Linux kernel. He currently maintains Xen support in Qemu, PV on HVM in the Linux kernel and libxenlight. Before joining Citrix he was a researcher at the Institute for Human and Machine Cognition, working on mobile ad hoc networks.
Traditionally Linux has always run on Xen either as a pure PV guest or as a virtualization unaware guest in an HVM domain. Recently, under the name of "PV on HVM", a series of works has been done to make Linux aware that is running on Xen and enable as many PV interfaces as possible even when running in an HVM container. After enabling the basic PV network and disk drivers, some other more interesting optimizations were implemented: in particular remapping legacy interrupts and MSIs onto event channels. This talk will explain the idea behind the feature, the reason why avoiding interactions with the lapic is a good, and some implementation details.