Virtual I/O Internals
The following document will attempt to detail the internals of a Virtual Function IO (VFIO) driven Mediated Device (Mdev).
RPC Mode | SR-IOV Mode |
---|---|
Host requires insight about guest of workload. | Host ignorance of guest workload. |
Error reporting. | No guest driver error reporting. |
In depth dynamic monitoring. | Basic dynamic monitoring. |
Software defined MMU guest separation. | Firmware defined MMU guest separation. |
Requires deferred instructions to be supported by host software (support libraries). | Guest is ignorant of host supported software such as support libraries. |
RPC Mode
Instruction Execution
RPC Mode moves instruction information across a virtual function interface (VF) using Remote Procedure Calls generally by way of soft interrupt (IOCTLs). Guest GPU instructions passed from the guest as Remote Procedure Calls are Just-in-time recompiled on the host for execution by a device driver.
Memory Management
Guests are presented with emulated memory regions (indirect emulated communication requiring a VM-exit) or passthrough memory regions (direct communication requiring no VM-exit).
RPC Mode Requirements:
Sensitive Instruction List.
Instruction Shim/Binary Translator.
HPA<->GPA Boundary Enforcement.
SR-IOV Mode
SR-IOV Mode involves the communication of instructions from a virtual function (VF) through direct communication to the PCI BAR.
RPC Mode Requirements:
Device SR-IOV support.
HPA<->GPA Boundary Enforcement.