1 files changed, 46 insertions, 0 deletions
diff --git a/debug/risc-v-gsp-rm-vm/sim/devices/pmu.py b/debug/risc-v-gsp-rm-vm/sim/devices/pmu.py
new file mode 100644
index 0000000..b241c7e
--- /dev/null
+++ b/debug/risc-v-gsp-rm-vm/sim/devices/pmu.py
@@ -0,0 +1,46 @@
+"""PMU stub.
+
+Evidence kind: **none yet** (no PMU register has been observed in the
+570.144 boot runs, and no PMU register semantics are needed to reach the
+rungs achieved so far).  The class exists so a profile can attach a PMU
+window without inventing behaviour: every access stays unhandled and is
+reported by the machine's unknown log, and the stub records the accesses it
+saw for later identification.
+
+When PMU accesses are observed, each register is added here with its header
+field evidence and a test, exactly like the falcon block.
+"""
+from __future__ import annotations
+
+from .base import Device
+
+
+class PmuStub(Device):
+    """A PMU window with no proven semantics: observe, never fake."""
+
+    name = "pmu"
+
+    def __init__(self, *, base: int = 0, size: int = 0x1000):
+        super().__init__(base=base, size=size)
+        self.reset()
+
+    def reset(self) -> None:
+        self.seen: dict[str, int] = {}
+
+    def read(self, offset: int, size: int) -> int | None:
+        self._note(offset, size, "r")
+        return None
+
+    def write(self, offset: int, size: int, value: int) -> bool:
+        self._note(offset, size, "w")
+        return False
+
+    def peek(self, offset: int, size: int) -> int | None:
+        return None
+
+    def _note(self, offset: int, size: int, rw: str) -> None:
+        key = f"{rw}:{offset:#x}:{size}"
+        self.seen[key] = self.seen.get(key, 0) + 1
+
+    def state(self) -> dict:
+        return {"seen": dict(sorted(self.seen.items()))}