Add getting started document for virtio machine.

Prepared it based on 5_1_x86_Emulation_and_Hardware.md file.

Bug-AGL: SPEC-3778
Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
Change-Id: I1688b4e24a18b0d33f008085c90411723a29b76a
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/documentation/+/25965
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Tested-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>

2 files changed, 154 insertions, 3 deletions

diff --git a/docs/0_Getting_Started/2_Building_AGL_Image/5_0_Building_the_AGL_Image.md b/docs/0_Getting_Started/2_Building_AGL_Image/5_0_Building_the_AGL_Image.md
index a891ef1..1573b56 100644
--- a/docs/0_Getting_Started/2_Building_AGL_Image/5_0_Building_the_AGL_Image.md
+++ b/docs/0_Getting_Started/2_Building_AGL_Image/5_0_Building_the_AGL_Image.md
@@ -12,10 +12,10 @@ The previous sections in the "Image Development Workflow" have treated this setu
 in a generic fashion. AGL has both `Qt` based and `HTML5` based IVI demos, where in the build process is almost the same except few changes in the build enviroment.
 
 This section, provides links to topics with instructions needed to create images for
-three types of supported platforms and for emulation using Quick EMUlator (QEMU)
-or VirtualBox:
+three types of supported platforms and for emulation/virtualization using Quick
+EMUlator (QEMU) or VirtualBox:
 
 * [x86 (Emulation and Hardware)](./5_1_x86_Emulation_and_Hardware.md)
 * [Raspberry Pi 4](./5_2_Raspberry_Pi_4.md)
 * [R Car Gen 3](./5_3_RCar_Gen_3.md)
-
+* [virtio](./5_4_Virtio.md)
diff --git a/docs/0_Getting_Started/2_Building_AGL_Image/5_4_Virtio.md b/docs/0_Getting_Started/2_Building_AGL_Image/5_4_Virtio.md
new file mode 100644
index 0000000..3a55fb2
--- /dev/null
+++ b/docs/0_Getting_Started/2_Building_AGL_Image/5_4_Virtio.md
@@ -0,0 +1,151 @@
+---
+title: Building for virtio
+---
+
+Virtio is a standartized interface for implementing virtual I/O devices:
+
+* Russell, Rusty. "virtio: towards a de-facto standard for virtual I/O devices." ACM SIGOPS Operating Systems Review 42.5 (2008): 95-103.
+
+This section describes the steps you need to take to build the AGL demo image
+for virtio "platform". Later, the same image can be run on various emulators or
+hypervisors that provide virtio devices, for example, QEMU aarch64 emulation on
+PC, QEMU/KVM aarch64 virtualization on AGL Reference Hardware, etc.
+
+Below, AGL minimal image and Qt based IVI demo are used as example, but
+similiarly one can run HTML5 based demos, cluster demo, or other AGL images.
+
+## 1. Making Sure Your Build Environment is Correct
+
+The
+"[Initializing Your Build Environment](./3_Initializing_Your_Build_Environment.md)"
+section presented generic information for setting up your build environment
+using the `aglsetup.sh` script.
+If you are building the AGL demo image for virtio platform, you need to specify
+some specific options when you run the script:
+
+```sh
+$ source meta-agl/scripts/aglsetup.sh -m virtio-aarch64 -b build-virtio-aarch64 agl-demo
+```
+
+The "-m" option specifies the "virtio-aarch64" machine.
+
+The "-b" option sets custom build directory instead of default "build".
+
+The "-f" option might be added to override previously available configuration.
+By default, if there were already configuration files in build directory, they
+will not be overriden, as result, aglsetup.sh might not have desired effect.
+
+## 2. Using BitBake
+
+This section shows the `bitbake` command used to build the AGL image.
+
+Start the build using the `bitbake` command.
+
+**AGL minimal image :**
+The target is `agl-image-minimal`.
+
+```sh
+$ bitbake agl-image-minimal
+```
+
+**Qt Based IVI demo :**
+The target is `agl-demo-platform`.
+
+```sh
+$ bitbake agl-demo-platform
+```
+
+## 3. Deploying the AGL Demo Image
+
+This subsection describes AGL virtio-aarch64 image deployment under virtio
+platform provided by QEMU aarch64 emulator on PC, or QEMU/KVM hypervisor on AGL
+Reference Hardware board.
+
+**3.1 QEMU on PC**
+
+If shell from which AGL was built is closed, or new shell is opened, then it is
+needed to re-initialize build environment:
+
+```sh
+$ source $AGL_TOP/build-virtio-aarch64/agl-init-build-env
+```
+
+And further use `runqemu` to boot the image :
+
+```sh
+$ runqemu
+```
+
+**3.2 QEMU/KVM on AGL Reference Hardware**
+
+Follow these steps to run virtual AGL on bare-metal AGL (AGL-in-AGL) on AGL Reference Hardware board:
+
+  1. Partition eMMC or SD-Card to have two partitions, at least 1 GiB each.
+    Actually, can be less but just rounded up to have a nice number.
+
+  2. Flash AGL minimal image root file system to the second partition on SD-Card
+    or eMMC.
+
+  3. Build AGL minimal image for AGL Reference Hardware.
+
+    ```sh
+    source meta-agl/scripts/aglsetup.sh -m h3ulcb -b build-h3ulcb agl-refhw-h3
+    ```
+
+    In `build-h3ulcb/conf/local.conf` add
+
+    ```
+    AGL_DEFAULT_IMAGE_FSTYPES = "ext4"
+    IMAGE_INSTALL_append = "qemu"
+    ```
+
+    CAUTION: Calling aglsetup.sh with "-f" flag will remove above modification
+    in "local.conf", so they will be needed to be re-applied.
+
+    Build image:
+
+    ```sh
+    bitbake agl-image-minimal
+    ```
+
+    Add virtio kernel to the AGL Reference Hardware Linux rootfs:
+
+    ```sh
+    cp build-virtio-aarch64/tmp/deploy/images/virtio-aarch64/Image build-h3ulcb/tmp/work/h3ulcb-agl-linux/agl-image-minimal/1.0-r0/rootfs/linux2
+    bitbake agl-image-minimal -c image_ext4 -f
+    bitbake agl-image-minimal -c image_complete
+    ```
+
+    Flash root file system to the first partition on SD-Card or eMMC.
+
+  4. Boot AGL Reference Hardware board using Linux located on the first partition of SD-Card or eMMC.
+
+  5. Run QEMU from Linux 1 command line
+
+    ```sh
+    qemu-system-aarch64 \
+      -machine virt \
+      -cpu cortex-a57 \
+      -m 2048 \
+      -serial mon:stdio \
+      -global virtio-mmio.force-legacy=false \
+      -drive id=disk0,file=/dev/mmcblk0p2,if=none,format=raw \
+      -device virtio-blk-device,drive=disk0 \
+      -object rng-random,filename=/dev/urandom,id=rng0 \
+      -device virtio-rng-device,rng=rng0 \
+      -nographic \
+      -kernel /linux2
+      -append 'root=/dev/vda rw mem=2048M'
+    ```
+
+    NOTE: mmcblk0p2 above is used for when root file system is flashed on eMMC.
+    In case of SD-Card, mmcblk1p2 has to be used.
+
+  6. It is possible to exit from QEMU using monitor commands. Enter "Ctrl+a h" for help.
+
+Know issue: to enable hardware virtualization using KVM, option `-enable-kvm`
+could be added to QEMU command line, but it fails with:
+
+```
+qemu-system-aarch64: kvm_init_vcpu failed: Invalid argument
+```