xv6-riscv64 on RP2350

About

A lightweight 64-bit RISC-V software emulator and bare-metal port that runs the xv6-riscv teaching operating system on the RP2350 (Raspberry Pi Pico 2) using only its on-chip SRAM. It emulates the Sv39 MMU, a 16550 UART, CLINT, PLIC and a VirtIO block device with a sector cache, so xv6 can boot to a shell and run user utilities such as ls and echo. The guest RAM footprint is 416 KB, which fits within the chip's 520 KB of SRAM without external PSRAM.