examples/virtio: initial README

examples/virtio/README.md

@@ -0,0 +1,61 @@
+# Using virtIO with multiple Linux guests
+
+This example shows off the virtIO support that libvmm provides using the
+[seL4 Device Driver Framework](https://github.com/au-ts/sddf) to talk to the
+actual hardware.
+
+The example currently works on the following platforms:
+* QEMU ARM virt
+
+## Building
+
+```sh
+make BOARD=<BOARD> MICROKIT_SDK=/path/to/sdk
+```
+
+Where `<BOARD>` is one of:
+* `qemu_arm_virt`
+
+Other configuration options can be passed to the Makefile such as `CONFIG`
+and `BUILD_DIR`, see the Makefile for details.
+
+If you would like to simulate the QEMU board you can run the following command:
+```sh
+make BOARD=qemu_arm_virt MICROKIT_SDK=/path/to/sdk qemu
+```
+
+This will build the example code as well as run the QEMU command to simulate a
+system running the whole system.
+
+## Running
+
+### virtIO console
+
+This example makes use of the virtIO console device so that neither guest has access
+to any serial device on the platform. The virtIO console support in libvmm talks to
+a serial multiplexor which then talks to a driver for input/output to the physical
+serial device.
+
+When you boot the example, you will see different coloured output for each guest. The
+Linux logs will be interleaving like so:
+```
+Starting klogd: OKStarting klogd: 
+OK
+Running sysctl: Running sysctl: OK
+OKSaving random seed: 
+Saving random seed: [    4.070358] random: crng init done
+[    4.103992] random: crng init done
+OK
+Starting network: OK
+Starting network: OK
+OK
+
+Welcome to Buildroot
+buildroot login: 
+Welcome to Buildroot
+buildroot login:
+```
+
+You will notice that we have two Buildroot login prompts, initially all input is defaulted
+to the guest one (in red). To switch to input into the other guest (green), type in `@2`.
+The `@` symbol is used to switch between clients, in this case the green guest is client 2.