Module virtio 

Virtio subsystem – transport layer and device drivers.

This module provides the virtio transport abstraction for VeridianOS, supporting two transport backends:

• PCI transport (VirtioPciTransport): Used on x86_64, where virtio devices appear as PCI devices with vendor ID 0x1AF4 (Red Hat). The driver accesses device registers via BAR0 I/O port space.

• MMIO transport (mmio::VirtioMmioTransport): Used on AArch64 and RISC-V, where QEMU’s virt machine exposes virtio devices as memory-mapped regions starting at 0x0A00_0000.

Both transports are unified behind the VirtioTransport enum, which provides a common interface for device initialization, feature negotiation, queue setup, and notification.

Architecture

  VirtioTransport (enum)
    |-- Pci(VirtioPciTransport)      -- x86_64 via I/O ports (BAR0)
    |-- Mmio(VirtioMmioTransport)    -- AArch64/RISC-V via MMIO
    |
    +-- VirtQueue (queue.rs)         -- split virtqueue (shared)
    +-- VirtioBlkDevice (blk.rs)     -- block device driver (shared)

Legacy PCI Layout (BAR0 I/O Space)

The PCI transport uses the legacy (transitional) virtio PCI interface as described in the virtio 1.0 specification, section 4.1:

Offset	Size	Name
0x00	4	device_features
0x04	4	guest_features
0x08	4	queue_address
0x0C	2	queue_size
0x0E	2	queue_select
0x10	2	queue_notify
0x12	1	device_status
0x13	1	isr_status
0x14+	var	device config

For the MMIO register layout, see mmio.

Modules

blk

Virtio-blk device driver

mmio

Virtio MMIO transport (virtio 1.0 legacy-compatible)

queue

Split virtqueue implementation for virtio devices.

regs

Legacy virtio PCI register offsets (I/O space via BAR0)

status

Virtio device status flags (virtio spec 2.1)

Structs

VirtioPciTransport

Virtio PCI transport handle.

Enums

VirtioTransport

Unified transport enum for virtio-blk

Constants

VIRTIO_BLK_DEVICE_ID_LEGACY

Virtio-blk PCI device IDs Legacy device ID (virtio 0.9 / transitional)

VIRTIO_BLK_DEVICE_ID_MODERN

Modern device ID (virtio 1.0+, transitional)

VIRTIO_VENDOR_ID

Virtio vendor ID (Red Hat, Inc.)