Implement VSTOPI CSR for RISC-V

Author: KushalMeghani1644

riscv/src/register.rs

@@ -63,6 +63,7 @@ pub mod sepc;
 pub mod sip;
 pub mod sscratch;
 pub mod stval;
+pub mod vstopi;
 
 // Supervisor Protection and Translation
 pub mod satp;

riscv/src/register/vstopi.rs

@@ -0,0 +1,69 @@
+//! vstopi register — Virtual Supervisor Top Priority Interrupt (0xEB0)
+
+read_only_csr! {
+    /// Virtual Supervisor Top Priority Interrupt Register
+    Vstopi: 0xEB0,
+    mask: 0x0FFF_00FF,
+}
+
+read_only_csr_field! {
+    Vstopi,
+    /// Interrupt ID (bits 16..27)
+    ///
+    /// Identifies the specific interrupt source. A value of 0 indicates no interrupt is pending.
+    /// Non-zero values correspond to specific interrupt sources as defined by the interrupt controller.
+    iid: [16:27],
+}
+
+read_only_csr_field! {
+    Vstopi,
+    /// Interrupt Priority ID (bits 0..7)
+    ///
+    /// Represents the priority level of the pending interrupt.
+    /// Lower numerical values indicate higher priority interrupts.
+    iprio: [0:7],
+}
+
+impl Vstopi {
+    /// Returns true if there is a valid interrupt pending
+    ///
+    /// When this returns true, both `interrupt_id()` and `priority()` will return meaningful values.
+    #[inline]
+    pub fn is_interrupt_pending(&self) -> bool {
+        self.iid() != 0
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_vstopi_fields() {
+        let vstopi = Vstopi::from_bits(0);
+        test_ro_csr_field!(vstopi, iid: [16, 27], 0x0);
+        test_ro_csr_field!(vstopi, iprio: [0, 7], 0x0);
+
+        let vstopi = Vstopi::from_bits((0xB << 16) | 5);
+        test_ro_csr_field!(vstopi, iid: [16, 27], 0xB);
+        test_ro_csr_field!(vstopi, iprio: [0, 7], 0x5);
+
+        let vstopi = Vstopi::from_bits((0xFFF << 16) | 0xFF);
+        test_ro_csr_field!(vstopi, iid: [16, 27], 0xFFF);
+        test_ro_csr_field!(vstopi, iprio: [0, 7], 0xFF);
+
+        let vstopi = Vstopi::from_bits(1 << 16);
+        test_ro_csr_field!(vstopi, iid: [16, 27], 0x1);
+        test_ro_csr_field!(vstopi, iprio: [0, 7], 0x0);
+
+        let vstopi = Vstopi::from_bits(1);
+        test_ro_csr_field!(vstopi, iid: [16, 27], 0x0);
+        test_ro_csr_field!(vstopi, iprio: [0, 7], 0x1);
+    }
+
+    #[test]
+    fn test_vstopi_bitmask() {
+        let vstopi = Vstopi::from_bits(usize::MAX);
+        assert_eq!(vstopi.bits(), 0x0FFF_00FFusize);
+    }
+}