Google Gets Serious About Android on RISC-V, Releases a Rough Roadmap to Emulator Availability

Google has confirmed that Android devices powered by the free and open RISC-V instruction set architecture are coming — and have told developers to get ready, as it moves what was previously a bunch of disconnected third-party experiments into the mainstream.

"Android is an open source operating system that is freely available to port to many devices and architectures. As such it supports many different device types and CPU architectures. We’re excited to be adding a new one to that list: RISC-V," Google's Lars Bergstrom and Greg Simon write in a joint statement.

"RISC-V is a free and open instruction set architecture (ISA)," the pair continue, "bringing the same spirit of industry-wide collaboration and innovation that we see in software around open source to the hardware ecosystem. Invented 10 years ago at the University of California, Berkeley, RISC-V has seen rapid adoption in embedded and microcontroller spaces, and in recent years has expanded into accelerators, servers, and mobile computing."

The first unofficial stirrings of RISC-V support in the Android operating system came from PLCT Lab's Chen Wang, who showed off an Android Open-Source Project (AOSP) minimal boot on an emulated RISC-V core back in November 2020. A few months later, Alibaba's T-Head division — which designs and produces commercial chips based on the RISC-V architecture — showed off a more functional Android 10 port, followed a year later by Android 12.

Google, though, was relatively silent on the matter — but has now confirmed that RISC-V-powered Android devices are on the way, following its announcement of official support at the RISC-V Summit in November last year. "The latest update that we have is that now not only are we accepting patches," Bergstrom and Simon write, "but we have begun to mature support for RISC-V in Android."

That maturation includes locking down exactly what version of the architecture will be needed for a device to support Google's official Android releases. "RISC-V is a modular ISA, meaning that there are a large number of optional extensions," the pair explain. "We have also determined an initial set that we feel is critical to ensure that any CPU running RISC-V will have all of the features we expect to achieve high performance. This set includes the rva22 profile as well as the vector and vector crypto extensions.

"Anyone wanting to experiment with Android on RISC-V now can do so, even without RISC-V hardware: Google has added support for building and running the Android Open Source Project using a RISC-V virtual target via the Cuttlefish Virtual Device system — providing a graphical interface over VNC. "At this time, these patches will support building and running a basic Android Open Source Project experience," the pair warn, "but are not yet fully optimized."

Google's public roadmap for the effort includes the promise of fully-featured emulators available for public release by 2024, initially focusing on RISC-V-powered wearables as per the company's recent partnership with Qualcomm, and from there to collaborate with the RISC-V Software Ecosystem (RISE) project to accelerate the development and release of software targeting high-performance application-class RISC-V processors.

More details, and instructions on trying the RISC-V AOSP build out via Cuttlefish, are available in Google's blog post.