sbi-testing: mark that only RV64 is supported by now

TODO support RV32 instruction set for sbi-testing

Signed-off-by: Zhouqi Jiang <luojia@hust.edu.cn>

.github/workflows/ci.yml

@@ -112,7 +112,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        TARGET: [riscv64imac-unknown-none-elf, riscv32imac-unknown-none-elf]
+        TARGET: [riscv64imac-unknown-none-elf] #, riscv32imac-unknown-none-elf]
     steps:
       - uses: actions/checkout@v4
       - uses: actions-rust-lang/setup-rust-toolchain@v1

sbi-testing/src/thread.rs

@@ -78,6 +78,7 @@ impl Thread {
         const INTERRUPT_BIT: usize = 1 << 5;
         sstatus |= PREVILEGE_BIT | INTERRUPT_BIT;
         // 执行线程
+        // TODO support RV32 instruction set
         core::arch::asm!(
             "   csrw sscratch, {sscratch}
                 csrw sepc    , {sepc}