feat(sbi): 重写上下文切换

Author: YdrMaster

rustsbi-qemu/src/execute/mod.rs

@@ -1,7 +1,7 @@
 use crate::{clint, hart_id, Supervisor};
 
 #[repr(C)]
-#[derive(Default)]
+#[derive(Debug)]
 struct Context {
     msp: usize,
     x: [usize; 31],
@@ -11,7 +11,7 @@ struct Context {
 
 pub(crate) fn execute_supervisor(supervisor: Supervisor) {
     use core::arch::asm;
-    use riscv::register::{medeleg, mie, mstatus};
+    use riscv::register::{medeleg, mie, mip, mstatus};
 
     unsafe {
         mstatus::set_mpp(mstatus::MPP::Supervisor);
@@ -46,7 +46,7 @@ pub(crate) fn execute_supervisor(supervisor: Supervisor) {
 
     loop {
         use crate::qemu_hsm::{EID_HSM, FID_HART_STOP, FID_HART_SUSPEND, SUSPEND_NON_RETENTIVE};
-        use riscv::register::mcause::{self, Exception as E, Trap as T};
+        use riscv::register::mcause::{self, Exception as E, Interrupt as I, Trap as T};
 
         unsafe { m_to_s(&mut ctx) };
 
@@ -66,14 +66,23 @@ pub(crate) fn execute_supervisor(supervisor: Supervisor) {
                 *ctx.a_mut(1) = ans.value;
                 ctx.mepc = ctx.mepc.wrapping_add(4);
             }
+            T::Interrupt(I::MachineTimer) => unsafe {
+                mip::clear_mtimer();
+                mip::set_stimer();
+            },
+            T::Exception(E::IllegalInstruction) => {
+                println!("TODO emulate or forward illegal instruction");
+                break;
+            }
             t => {
                 println!("{t:?}");
-                loop {
-                    core::hint::spin_loop();
-                }
+                break;
             }
         }
     }
+    loop {
+        core::hint::spin_loop();
+    }
 }
 
 impl Context {

rustsbi-qemu/src/main.rs

@@ -170,7 +170,7 @@ extern "C" fn rust_main(_hartid: usize, opaque: usize) {
     }
 }
 
-/// 准备好深度休眠或关闭
+/// 准备好不可恢复休眠或关闭
 extern "C" fn finalize() {
     //! 在隔离的环境调用，以确保 main 中使用的堆资源完全释放
     HSM.wait().finallize_before_stop();

rustsbi-qemu/src/qemu_hsm.rs

@@ -99,30 +99,30 @@ impl QemuHsm {
     /// 此时核状态必然是不可干预的 Pending 状态，中断业已关闭。
     pub fn finallize_before_stop(&self) {
         use core::sync::atomic::Ordering::{AcqRel, Acquire};
-        use riscv::register::{mie, mip};
+        use riscv::register::mie;
 
         // 检查当前状态是重启前的挂起状态
         let state = &self.state[hart_id()];
         let current = state.load(Acquire);
         let new: u8 = match current {
-            STOP_PENDING => STOPPED,
-            SUSPEND_PENDING => SUSPEND,
+            STOP_PENDING => {
+                // 一旦关闭，只能通过软件中断重启
+                unsafe { mie::clear_mext() };
+                STOPPED
+            }
+            SUSPEND_PENDING => {
+                // 休眠也可以通过外部中断唤醒
+                unsafe { mie::set_mext() };
+                SUSPEND
+            }
             s => panic!("wrong state {s:?}!"),
         };
-
-        // TODO: SBI 在 M 态应该总是处于这样干净的状态，即：
-        // 1. 所有中断标记清除
-        // 2. 所有中断已关闭
-        //
-        // 这样，发生状态转换时只需要：
-        // 1. 重设 mtvec
-        // 2. 开启需要的中断
-        self.clint.clear_soft(hart_id());
+        // 通过软件中断重启
         unsafe {
-            mip::clear_msoft();
             mie::set_msoft();
-            set_mtcev(entry as _);
-        }
+            set_mtcev(entry as _)
+        };
+        // 转移状态
         if let Err(unexpected) = state.compare_exchange(current, new, AcqRel, Acquire) {
             panic!("failed to reboot for a race {current:?} => {unexpected:?}")
         }

test-kernel/src/main.rs

@@ -109,8 +109,8 @@ extern "C" fn primary_rust_main(hartid: usize, dtb_pa: usize) -> ! {
     test::base_extension();
     test::sbi_ins_emulation();
 
-    unsafe { stvec::write(start_trap as usize, TrapMode::Direct) };
-    test::trap_delegate(hartid);
+    // unsafe { stvec::write(start_trap as usize, TrapMode::Direct) };
+    // test::trap_delegate(hartid);
 
     println!();
     STARTED.fetch_add(1, Ordering::SeqCst);