[codex] Add SBI console input on RISC-V

[Jonesxq]

Summary

• replace per-byte RISC-V SBI console output with bulk console_write
• add default RISC-V console input through console_read, including readiness caching and async stdin polling
• enable the default RISC-V stdin CI test

Why

The default RISC-V console only supported output through console_write_byte and never read input, so stdin could not work. The SBI debug console extension provides bulk read and write operations that address both limitations.

The SBI API accepts physical addresses, so the console uses a page-aligned bounce buffer embedded in the serial device. Kernel data is identity-mapped on RISC-V; keeping the buffer local to the device also avoids page-table translation during early logging or while the page-table lock is held.

Impact

Default-console RISC-V guests can now receive stdin, and console output is sent in chunks instead of one SBI call per byte.

Validation

• built the RISC-V kernel and hermit-builtins
• ran repository-wide cargo xtask clippy across architectures and feature combinations
• cargo fmt --all -- --check
• git diff --check

Local QEMU stdin execution was not available because qemu-system-riscv64 is not installed. The RISC-V stdin CI job is enabled by this change.

Closes #1838

[github-actions]

Benchmark Results

Details

Benchmark	Current: 8f19f39	Previous: 2e23902	Performance Ratio
startup_benchmark Build Time	81.38 s	80.34 s	1.01 ❗
startup_benchmark File Size	0.79 MB	0.80 MB	1.00 ❗
Startup Time - 1 core	0.75 s (±0.02 s)	0.75 s (±0.02 s)	1.00
Startup Time - 2 cores	0.77 s (±0.02 s)	0.74 s (±0.02 s)	1.05 ❗
Startup Time - 4 cores	0.76 s (±0.02 s)	0.74 s (±0.02 s)	1.03
multithreaded_benchmark Build Time	81.60 s	82.11 s	0.99 ❗
multithreaded_benchmark File Size	0.90 MB	0.86 MB	1.05 ❗
Multithreaded Pi Efficiency - 2 Threads	87.81 % (±4.42 %)	85.89 % (±6.61 %)	1.02
Multithreaded Pi Efficiency - 4 Threads	42.66 % (±2.30 %)	43.43 % (±2.56 %)	0.98
Multithreaded Pi Efficiency - 8 Threads	24.66 % (±1.64 %)	25.76 % (±1.53 %)	0.96
micro_benchmarks Build Time	80.17 s	80.40 s	1.00 ❗
micro_benchmarks File Size	0.90 MB	0.86 MB	1.05 ❗
Scheduling time - 1 thread	64.19 ticks (±2.42 ticks)	62.65 ticks (±4.06 ticks)	1.02
Scheduling time - 2 threads	36.00 ticks (±5.11 ticks)	34.08 ticks (±4.10 ticks)	1.06
Micro - Time for syscall (getpid)	4.42 ticks (±0.81 ticks)	3.45 ticks (±0.58 ticks)	1.28
Memcpy speed - (built_in) block size 4096	84686.73 MByte/s (±58599.22 MByte/s)	82448.38 MByte/s (±56997.13 MByte/s)	1.03
Memcpy speed - (built_in) block size 1048576	30399.98 MByte/s (±24479.96 MByte/s)	30585.98 MByte/s (±24707.84 MByte/s)	0.99
Memcpy speed - (built_in) block size 16777216	29306.61 MByte/s (±24085.90 MByte/s)	26340.06 MByte/s (±21720.96 MByte/s)	1.11
Memset speed - (built_in) block size 4096	84033.61 MByte/s (±58226.21 MByte/s)	82292.76 MByte/s (±56891.50 MByte/s)	1.02
Memset speed - (built_in) block size 1048576	31110.92 MByte/s (±24903.36 MByte/s)	31323.85 MByte/s (±25145.86 MByte/s)	0.99
Memset speed - (built_in) block size 16777216	30065.44 MByte/s (±24522.27 MByte/s)	27104.68 MByte/s (±22209.94 MByte/s)	1.11
Memcpy speed - (rust) block size 4096	74968.57 MByte/s (±52503.01 MByte/s)	74097.96 MByte/s (±51811.44 MByte/s)	1.01
Memcpy speed - (rust) block size 1048576	30276.51 MByte/s (±24480.06 MByte/s)	30361.60 MByte/s (±24602.37 MByte/s)	1.00
Memcpy speed - (rust) block size 16777216	29442.22 MByte/s (±24206.78 MByte/s)	27625.34 MByte/s (±22806.88 MByte/s)	1.07
Memset speed - (rust) block size 4096	75551.56 MByte/s (±52899.66 MByte/s)	74373.47 MByte/s (±51976.48 MByte/s)	1.02
Memset speed - (rust) block size 1048576	31023.57 MByte/s (±24919.37 MByte/s)	31110.89 MByte/s (±25033.24 MByte/s)	1.00
Memset speed - (rust) block size 16777216	30174.50 MByte/s (±24616.23 MByte/s)	28386.93 MByte/s (±23265.03 MByte/s)	1.06
alloc_benchmarks Build Time	77.71 s	74.76 s	1.04 ❗
alloc_benchmarks File Size	0.87 MB	0.87 MB	1.00 ❗
Allocations - Allocation success	91.31 %	91.31 %	1
Allocations - Deallocation success	100.00 %	100.00 %	1
Allocations - Pre-fail Allocations	61.44 %	61.44 %	1
Allocations - Average Allocation time	4287.14 Ticks (±105.93 Ticks)	5860.58 Ticks (±98.43 Ticks)	0.73 ❗
Allocations - Average Allocation time (no fail)	5058.75 Ticks (±104.51 Ticks)	6554.81 Ticks (±92.86 Ticks)	0.77 ❗
Allocations - Average Deallocation time	945.96 Ticks (±226.80 Ticks)	1805.01 Ticks (±250.35 Ticks)	0.52 ❗
mutex_benchmark Build Time	78.64 s	79.82 s	0.99 ❗
mutex_benchmark File Size	0.90 MB	0.86 MB	1.05 ❗
Mutex Stress Test Average Time per Iteration - 1 Threads	12.22 ns (±0.46 ns)	12.10 ns (±0.41 ns)	1.01
Mutex Stress Test Average Time per Iteration - 2 Threads	40.12 ns (±2.03 ns)	40.26 ns (±1.68 ns)	1.00

This comment was automatically generated by workflow using github-action-benchmark.