guest-diag: reset per-client pin state when a new client pid appears

A new CUDA client allocates fresh channel pools at the same GPU VAs; the
watcher kept the previous client's sem kptrs and seen-pin marks, so it
pinned the previous (freed) pool pages and the new client's release writes
went to dead memory. Clear the learned sems/marks on each pid change.

1 files changed, 21 insertions, 0 deletions

diff --git a/tools/guest-diag/semfix_uvmt.py b/tools/guest-diag/semfix_uvmt.py
index b9f3ac9..636e1f4 100755
--- a/tools/guest-diag/semfix_uvmt.py
+++ b/tools/guest-diag/semfix_uvmt.py
@@ -69,6 +69,16 @@ class Stream:
         self.pbs = []
         self.new_pbs = []
 
+    def reset(self):
+        """Forget everything learned about the previous client. A new client
+        allocates its own channel pools; keeping the old sems/seen-pin marks
+        makes the watcher chase stale kernel pointers and pin the previous
+        client's (freed) pool pages - the stale-translation trap."""
+        self.sems = []
+        self.pbs = []
+        self.pids = []
+        self.new_pbs = []
+
     def poll(self):
         try:
             with open(self.path) as f:
@@ -290,6 +300,17 @@ def main():
             log("stream: new uvmt sem 0x%x" % s)
         for p in new_pids:
             log("stream: client pid %d" % p)
+            if last_pid is not None and p != last_pid:
+                stream.reset()
+                known_sems.clear()
+                seen_sem_pin.clear()
+                last_state.clear()
+                last_seen_t.clear()
+                pinned_ranges.clear()
+                seen_ch.clear()
+                seen_pb.clear()
+                counter_pids.clear()
+                log("semfix: new client pid %d - reset per-client pin state" % p)
             last_pid = p
         for pb in getattr(stream, "new_pbs", []):
             log("stream: new pushbuffer 0x%x" % pb)