tests: add mtval2 unit tests

Adds basic unit tests for the `mtval2` CSR.

Author: rmsyn

riscv/src/register/mtval2.rs

@@ -21,3 +21,22 @@ impl Mtval2 {
         self.bits() << Self::GUEST_PAGE_SHIFT
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_mtval2() {
+        (1..=usize::BITS)
+            .map(|r| ((1u128 << r) - 1) as usize)
+            .for_each(|bits| {
+                let mtval2 = Mtval2::from_bits(bits);
+                assert_eq!(mtval2.bits(), bits);
+                assert_eq!(
+                    mtval2.guest_fault_address(),
+                    bits << Mtval2::GUEST_PAGE_SHIFT
+                );
+            });
+    }
+}