GUO Ren
A Linux kernel developer focuses on the CPU subsystem, including virtualization, IOMMU, PCIe, Heterogeneous Programming, and RV64ILP32.
Staff Engineer, Alibaba Damo Academy
Sessions
Historically, several architectures have explored running ILP32 software on 64-bit ISAs - including ×86-X32, MIPS-N32, and Arm64-ILP32 - yet only Arm64-ILP32 reached commercial adoption, exclusively within Watch OS as a closed-source implementation.
We now present a new landmark: the first open-source commercial deployment of
RV64ILP32, realized on the Allwinner V881 Al Glasses SoC (Dual-Core XuanTie
(907).
1. Product-Level Demo (V881-based): An Al Glasses device running with
RV64ILP32 Linux kernel. Benchmarks against traditional RV32 Linux kernel demonstrate substantial gains - iperf loopback test throughput improves by 1.5×, while eBPF performance achieves up to 5.7× speedups across test cases
2. Community-Level Demo (QEMU-based): For the first time, LP64 applications execute on an RV64ILP32 Linux kernel, which provides ‡2 GB of separate address spaces, revealing new possibilities for mixed-ABI workloads on RISC-V (20% memory footprint saved v.s. traditional RV64 Linux kernel).
Together, these demonstrations mark a significant milestone: delivering 64-bit RISC-V performance advantages to resource-constrained embedded AI devices, while preserving ILP32 memory/cache efficiency - entirely on an open-source software stack.
The surging demand for VM-based secure containers in the AI Agent era is driving rapid growth in the scale of vCPU deployments. However, the current RISC-V AIA specification co-locates inter-processor interrupts (IPIs) and device interrupts within the IMSIC, causing hardware resource overhead to scale multiplicatively with both the per-file size and the total count of S/VS-files — a structural coupling that fundamentally limits vCPU interrupt pass-through scalability.
To address this, we propose the Software-interrupt MSI Controller (SMSIC), an AIA extension that explicitly decouples IPI from the IMSIC external interrupt hierarchy and establishes a dedicated MSI delivery path for the software interrupts defined in the RISC-V privileged specification. By fully decoupling the IPI path from the device interrupt path, SMSIC reduces the per-VS-file IPI resource to a single interrupt entry, comprising only one enable bit and one pending bit, thereby supporting large-scale VS-file deployment at minimal hardware cost (for both the per-hart and SoC IPI merging & absorption components). Furthermore, with the IPI path isolated, IOMMU MRIF can scale the number of virtualization interrupt files to support larger-scale deployments of vCPU interrupt pass-through, effectively taking over the scalability role from native IMSIC VS-files.
The increasing computational demands of modern AI workloads necessitate a holistic architectural approach to AI acceleration on RISC-V processors. This talk presents the XuanTie Tensor Processing Engine (TPE), a RISC-V-based Attached Matrix Extension (AME) engine designed to address AI acceleration across three dimensions: ISA, microarchitecture, and software ecosystem.
At the ISA level, the TPE adopts the in-progress RISC-V AME specification, featuring dedicated tensor registers and a comprehensive instruction set encompassing matrix multiply-accumulate, element-wise, special function, reduction, and load/store operations with broad data type support including INT4, FP8, FP16, and micro-scaling formats.
At the microarchitecture level, the design incorporates a matrix engine achieving 2 TOPS/GHz at INT8/FP8, a concurrent vector engine with hardware-accelerated non-linear functions, and a layered memory subsystem featuring a coherent tensor cache and data prefetch engine.
A full-stack software ecosystem spanning LLVM toolchain to graph execution runtime completes the solution.
Experimental results on the XuanTie C930 cluster demonstrate 99% FP16 GEMM utilization. We discuss key design trade-offs and implications for the evolving RISC-V AME standard.