QEMU roles

QEMU appears in this project as two different processes: the vhost that runs the guest, and a functional model that exports a PCI device. They have independent command lines and lifetimes.

Role One: vhost

The host QEMU runs guest Linux, the amdgpu driver and ROCm applications. It owns CPU, memory, the PCIe topology, direct kernel boot, and QMP and serial management. It maps the machine memory pool as guest RAM and attaches every device as a separate vfio-user client on a dedicated PCIe root port.

Role Two: device model

The device QEMU uses -machine x-remote and x-vfio-user-server to export one PCI device, for example the edu educational device shipped with QEMU. This mode is functional only; it suits protocol, driver and integration tests and provides no timing model.

Chapter Contents

• QEMU as vhost
• QEMU device models

Recommended Reading Path

• Read QEMU as vhost first for the guest runtime setup.

• Then read QEMU device models for the vfio-user functional device startup.

• For MI300X performance behavior, continue with gem5 performance simulation.

• For the system view of the connection protocol, see vfio-user interface.