Virtual I/O Internals

The following document will attempt to detail the internals of a Virtual Function IO (VFIO) driven Mediated Device (Mdev).

Requirements:

Sensitive Instruction List.

Instruction Shim/Binary Translator.

HPA<->GPA Boundary Enforcement.

RPC Mode

File:Mediated Device Access MMU.png

A slide describing Extended Page Table & MMU used in mediated device management.

RPC Mode moves instruction information across a virtual function interface (VF) using Remote Procedure Calls generally by way of soft interrupt (IOCTLs). These instructions are presented to the host in the context of emulated memory regions (indirect emulated communication, requires a VM-exit) or passthrough memory directions (direct communication, no VM-exit).

File:Mediated Device Access.png

A slide from Neo Gia's presentation at KVM forum.

SR-IOV Mode

SR-IOV Mode involves the communication of instructions from a virtual function (VF) though direct communication to the PCI BAR.