Add instructions for building and installing AVF on Pixel 6
... by the partners request.
Bug: N/A
Test: follow the instruction
Change-Id: I91cdb0a637d9018119dec2207b02c91f76812846
diff --git a/docs/getting_started/pixel6.md b/docs/getting_started/pixel6.md
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+# Instructions for building custom AVF on Pixel 6 or 6 Pro
+
+This document provides steps for building AVF from AOSP, and then install it to
+Pixel 6 series to better understand AVF and do some experiments.
+
+**WARNING**: Unless Android 13 is released to AOSP (expected to be at Summer
+2022, exact date TBD) by the time when you read this documentation, or you or
+your company have early access to Android Tiramisu source tree, you **CANNOT**
+follow this instruction. In that case, you can only **USE** the AVF that is
+shipped in the Android 13 Beta Image.
+
+This is because AVF in the beta image is signed by Google and therefore it can't
+be updated to a new AVF built in AOSP which can't be signed by the Google key
+that is not shared with AOSP.
+
+## Upgrade to Android 13 Beta Image
+
+First, upgrade your Pixel 6 or Pixel 6 Pro to the Android 13 Beta Image. This
+can be done in two ways:
+
+* Join [Android Beta Program](https://www.google.com/android/beta) and then OTA
+ to Android 13.
+* Manually flash [Android 13 Beta Images](https://developer.android.com/about/versions/13/download#factory-images).
+
+Then enable ADB debugging in "Settings" -> "System" -> "Developer options".
+Finally, enable PKVM.
+
+```shell
+adb reboot bootloader
+fastboot flashing unlock
+fastboot oem pkvm enable
+fastboot reboot
+```
+
+## Building GSI and flashing it
+
+Prepare your Android 13 (Tiramisu) source tree.
+
+```shell
+mkdir tm
+cd tm
+repo init -u <URL> -m <your_tm_branch>
+repo sync -c --no-tags -j 10
+```
+
+Patch GSI so that it includes AVF. Edit
+`build/make/target/product/gsi_release.mk` and add the following line to the
+end (or anywhere in the file that makes sense):
+
+```
+PRODUCT_PACKAGES += com.android.virt
+```
+
+Build GSI.
+
+```shell
+source build/envsetup.sh
+choosecombo 1 aosp_arm64 userdebug
+m
+```
+
+Flash GSI to the Pixel device.
+
+```shell
+adb reboot bootloader
+fastboot reboot fastboot
+fastboot delete-logical-partition product_a
+fastboot flash system out/target/product/generic_arm64/system.img
+fastboot --disable-verification flash vbmeta out/target/product/generic_arm64/vbmeta.img
+fastboot -w reboot
+```
+
+Deleting the logical partition `product_a` is needed because the GSI image is
+bigger than the logical partition `system_a` of the beta image.
+`--disable-verification` when flashing the `vbmeta` partition is critical. Don't
+miss it.
+
+Lastly, check if you are running GSI.
+
+```shell
+adb shell getprop ro.build.product
+adb shell ls /dev/kvm
+adb shell ls /apex/com.android.virt/bin/vm
+```
+
+The result should be as follows.
+
+```
+generic_arm64
+/dev/kvm
+/apex/com.android.virt/bin/vm
+```
+
+## Building and installing AVF from AOSP
+
+Checkout AOSP master branch.
+
+```shell
+mkdir aosp
+cd aosp
+repo init -u https://android.googlesource.com/platform/manifest -b master
+repo sync -c --no-tags -j 10
+```
+
+Then build the `com.android.virt` APEX.
+
+```shell
+source build/envsetup.sh
+banchan com.android.virt aosp_arm64
+UNBUNDLED_BUILD_SDKS_FROM_SOURCE=true m apps_only dist
+```
+
+Install the newly built AVF to the device
+
+```shell
+adb install out/dist/com.android.virt.apex
+adb reboot
+```
+
+If this doesn't work for some reason, try this:
+
+```
+adb root
+adb shell setenforce 0
+adb push out/dist/com.android.virt.apex /data/local/
+adb shell cmd -w apexservice deactivatePackage /system/system_ext/apex/com.android.virt.apex
+adb shell cmd -w apexservice activatePackage /data/local/com.android.virt.apex
+// Don't adb reboot
+```