diff --git a/spec/std/isa/ext/Zawrs.yaml b/spec/std/isa/ext/Zawrs.yaml
index 4ce17136ce..fc32106d19 100644
--- a/spec/std/isa/ext/Zawrs.yaml
+++ b/spec/std/isa/ext/Zawrs.yaml
@@ -18,6 +18,18 @@ description: |
   * Code waiting on a flag to be set in memory indicative of an event occurring.
     For example, software on a RISC-V hart may wait on a "done" flag to be set in memory by an
     accelerator device indicating completion of a job previously submitted to the device.
+params:
+  BOUNDED_TIME_LIMIT:
+    description: |
+      Defines the implementation-specific bounded time limit within which a wrs.nto instruction must complete.
+    schema:
+      type: integer
+  STO_DURATION:
+    description: |
+      Implementation-defined short timeout for wrs.sto instruction such that the stall is terminated on
+      the timeout if no other conditions have occurred to terminate the stall.
+    schema:
+      type: integer
 type: unprivileged
 versions:
   - version: "1.0.1"
diff --git a/spec/std/isa/inst/Zawrs/wrs.nto.yaml b/spec/std/isa/inst/Zawrs/wrs.nto.yaml
index 835c008c27..f07ef55e91 100644
--- a/spec/std/isa/inst/Zawrs/wrs.nto.yaml
+++ b/spec/std/isa/inst/Zawrs/wrs.nto.yaml
@@ -51,3 +51,18 @@ access:
   vu: always
 data_independent_timing: false
 operation(): |
+  if ((CSR[mstatus].TW == 1'b1) && (mode() != PrivilegeMode::M)) {
+    if (wait_on_reservation_set_bounded() == false) {
+      raise (ExceptionCode::IllegalInstruction, mode(), $encoding);
+    }
+  }
+  else if (CSR[misa].H == 1) {
+    if ((CSR[hstatus].VTW == 1'b1) && ((mode() == PrivilegeMode::VS) || (mode() == PrivilegeMode::VU))) {
+      if (wait_on_reservation_set_bounded() == false) {
+        raise (ExceptionCode::VirtualInstruction, mode(), $encoding);
+      }
+    }
+  }
+  else {
+    wait_on_reservation_set($encoding);
+  }
diff --git a/spec/std/isa/inst/Zawrs/wrs.sto.yaml b/spec/std/isa/inst/Zawrs/wrs.sto.yaml
index 4d1c26f93d..e0bad8c090 100644
--- a/spec/std/isa/inst/Zawrs/wrs.sto.yaml
+++ b/spec/std/isa/inst/Zawrs/wrs.sto.yaml
@@ -47,3 +47,4 @@ access:
   vu: always
 data_independent_timing: false
 operation(): |
+  wait_on_reservation_set($encoding);
diff --git a/spec/std/isa/isa/builtin_functions.idl b/spec/std/isa/isa/builtin_functions.idl
index 86a54d71c9..008835c130 100644
--- a/spec/std/isa/isa/builtin_functions.idl
+++ b/spec/std/isa/isa/builtin_functions.idl
@@ -511,6 +511,40 @@ builtin function wfi {
   }
 }
 
+builtin function wait_on_reservation_set {
+  arguments Bits<INSTR_ENC_SIZE> encoding
+  description {
+    Hint to temporarily stall execution
+    in a low-power state as long as:
+
+    * The reservation set is valid
+    * No pending interrupt is observed
+    * If "wrs.sto", STO_DURATION has not elapsed
+
+    A valid implementation is a no-op.
+    The model will advance the PC; this function does not need to.
+  }
+}
+
+# A special form of "wait_on_reservation_set" when "wrs.nto" must
+# complete within an implementation defined bounded time limit
+builtin function wait_on_reservation_set_bounded {
+  returns Boolean
+  description {
+    Hint to temporarily stall execution
+    in a low-power state as long as:
+
+    * The reservation set is valid
+    * No pending interrupt is observed
+    * BOUNDED_TIME_LIMIT has not elapsed
+
+    A valid implementation is a no-op.
+    The model will advance the PC; this function does not need to.
+
+    Returns false if BOUNDED_TIME_LIMIT exceeded, else true
+  }
+}
+
 builtin function pma_applies? {
   returns Boolean
   arguments