Setup RISC-V AP timer

ostd/src/arch/riscv/mod.rs

@@ -48,14 +48,14 @@ pub(crate) unsafe fn late_init_on_bsp() {
     // SAFETY: This is called before any IPI-related operation is performed.
     unsafe { irq::ipi::init() };
 
-    // SAFETY: We're on the BSP and we're ready to boot all APs.
-    unsafe { crate::boot::smp::boot_all_aps() };
-
     // SAFETY: This function is called once and at most once at a proper timing
     // in the boot context of the BSP, with no timer-related operations having
     // been performed.
     unsafe { timer::init() };
 
+    // SAFETY: We're on the BSP and we're ready to boot all APs.
+    unsafe { crate::boot::smp::boot_all_aps() };
+
     // SAFETY:
     // 1. All the system device memory have been removed from the builder.
     // 2. RISC-V platforms do not have port I/O.
@@ -82,6 +82,9 @@ pub(crate) unsafe fn init_on_ap() {
 
     // SAFETY: This is called before any IPI-related operation is performed.
     unsafe { irq::ipi::init_current_hart() };
+
+    // SAFETY: The caller ensures that this function is only called once here.
+    unsafe { timer::init_current_hart() };
 }
 
 /// Returns the frequency of TSC. The unit is Hz.

ostd/src/arch/riscv/timer/mod.rs

@@ -26,8 +26,8 @@ static TIMER_INTERVAL: AtomicU64 = AtomicU64::new(0);
 /// # Safety
 ///
 /// This function is safe to call on the following conditions:
-/// 1. It is called once and at most once at a proper timing in the boot context.
-/// 2. It is called before any other public functions of this module is called.
+///  1. It is called once and at most once at a proper timing in the boot context.
+///  2. It is called before any other public functions of this module is called.
 pub(super) unsafe fn init() {
     TIMEBASE_FREQ.store(
         DEVICE_TREE
@@ -60,6 +60,16 @@ pub(super) unsafe fn init() {
         timer_irq
     });
 
+    // SAFETY: The caller ensures that this is only called once on the boot hart.
+    unsafe { init_current_hart() };
+}
+
+/// Initializes the timer on the current hart.
+///
+/// # Safety
+///
+/// This function must be called in a hart that hasn't called this function.
+pub(super) unsafe fn init_current_hart() {
     set_next_timer();
     // SAFETY: Accessing the `sie` CSR to enable the timer interrupt is safe
     // here because this function is only called during timer initialization,