QEMU RISC-V 32 bit `virt` Platform

This board crate targets the QEMU RISC-V 32 bit virt platform. It can utilize paravirtualized peripherals through the VirtIO transport. Currently supported periphals of this board are:

the primary 16550-compatible UART
VirtIO-based network adapters
VirtIO-based random number generators

While this target does not feature many peripherals for now, it represents a stable QEMU target for using Tock in a virtualized RISC-V environment. This can be useful for CI and other purposes. In the future, this target can be extended to support VirtIO peripherals.

Running QEMU

To run the board in QEMU, qemu-system-riscv32 must be started with the -machine virt argument. The Tock kernel expects to be loaded as the BIOS by passing -bios $TOCK_KERNEL.bin, such that it runs in RISC-V machine mode and has full control over the virtual board. -nographic can be used to suppress QEMU's graphical interface.

The [Makefile] further contains two targets for running this board's kernel in QEMU standalone, or with a single app. These can be executed through the run and run-app targets, respectively.

run: Start Tock on an emulated QEMU board without an app:

    Finished `release` profile [optimized + debuginfo] target(s) in 0.08s
   text    data     bss     dec     hex filename
  87552      48   41940  129540   1fa04 target/riscv32imac-unknown-none-elf/release/qemu_rv32_virt

Running QEMU emulator version 10.0.2 (tested: 8.2.7, 9.1.3; known broken: <= 8.1.5, >= 9.2.3) with
  - kernel target/riscv32imac-unknown-none-elf/release/qemu_rv32_virt.elf
To exit type C-a x

qemu-system-riscv32 \
  -machine virt \
  -semihosting \
  -global driver=riscv-cpu,property=smepmp,value=true \
  -global virtio-mmio.force-legacy=false \
  -device virtio-rng-device  \
  -nographic \
  -bios target/riscv32imac-unknown-none-elf/release/qemu_rv32_virt.elf
QEMU RISC-V 32-bit "virt" machine, initialization complete.
- Found VirtIO EntropySource device, enabling RngDriver
- VirtIO NetworkCard device not found, disabling EthernetTapDriver
Entering main loop.
tock$

run-app: Start Tock on an emulated QEMU board with an app:

tock/boards/qemu_rv32_virt $ make run-app APP=$PATH_TO_APP.tbf

Through the NETDEV environment variable, QEMU can be instructed to attach a VirtIO-based network adapter to the target. The following options are available:

NETDEV=NONE (default): Do not expose a network adapter to the guest.
NETDEV=SLIRP: Use QEMU's userspace networking capabilities (through libslirp), which provides the target with an emulated network and a gateway bridging outgoing TCP and UDP connections onto sockets of the host operating system. NETDEV_SLIRP_ARGS can be used to pass further arguments to the netdev, for instance to forward ports from host to guest. For example, to forward the TCP port 8080 to the guest at 192.168.1.50:80, use the following command line:
```
$ make run NETDEV=SLIRP NETDEV_SLIRP_ARGS=hostfwd=tcp::8080-192.168.1.50:80
```
NETDEV=TAP: Create a TAP network device on the host and expose the corresponding remote end to the guest's VirtIO network card. This establishes a layer-2 link between the host and guest. This option assumes that QEMU has the necessary permissions to use (or create) the device on the host. The interface will be unconfigured and needs to be made active and be assigned an IP address manually.
NETDEV=SUDO-TAP: Like TAP, but run QEMU as root through sudo. This will likely prompt for a password.

README

QEMU RISC-V 32 bit virt Platform

Running QEMU

QEMU RISC-V 32 bit `virt` Platform