tools: transport-proof demand writes + tolerant demand parsing (the pool-pin latency root cause)

The r581 boot's guest scanner died mid-boot with ValueError in main():
"invalid literal for int() with base 16:
'0x20400f000\\n0x121000000\\n0x12000ab4c'". A guest-agent transport-escaped
append merged demand VAs onto one line with literal backslash-n, and the
old parser crashed on it. The crash stopped ALL new pins; the host only
re-asserted known pairs, so the UVM pool VA 0x121000000 never arrived
while 185 other injections flowed - the pool-pin latency that blocked
every validation boot.

* pin_gr_stream._demand_send/_demand_loop now write one "echo <va> >>"
  per VA (no newlines, no backslashes in the transported command; immune
  to transport escaping).
* guest_pin_stream's demand parser extracts every 0x token with re and
  skips malformed ones instead of raising out of main().

1 files changed, 22 insertions, 4 deletions

diff --git a/tools/guest-diag/pin_gr_stream.py b/tools/guest-diag/pin_gr_stream.py
index 6eb5be7..ff7e299 100644
--- a/tools/guest-diag/pin_gr_stream.py
+++ b/tools/guest-diag/pin_gr_stream.py
@@ -100,15 +100,33 @@ def _scanner_alive():
     return "ALIVE" in (out or "")
 
 
+def _demand_write_cmd(vas):
+    """Build a transport-proof append command for the guest demand file.
+
+    r582: the old `printf '%s' '<lines with real LF>'` form was mangled by
+    the guest-agent transport under load - the newlines arrived as LITERAL
+    backslash-n text and merged VAs onto one line, and the guest scanner's
+    parser then crashed on `int('0x20400f000\\\\n0x121000000...', 16)`
+    (ValueError in main; r581 boot scanner log). The scanner's death stopped
+    ALL new pins while the host only re-asserted known pairs - the observed
+    pool-pin-latency (0x121000000 never arrived while other injections
+    flowed). One `echo <va> >> file` per VA carries no newlines and no
+    backslashes at all, so no transport layer can escape them."""
+    return "; ".join("echo 0x%x >> /tmp/guest_want_vas.txt" % va
+                     for va in vas)
+
+
 def _demand_send(vas):
     """Append VA hints to the guest scanner's demand file (best-effort).
 
     Same channel pin_gr_stream._demand_loop uses for host-dmesg stalls; the
     stall watchdog uses it to ask the scanner to re-resolve the fixed
     pre-capture VAs (counter page / UVM pool) by content/pagemap."""
-    lines = "".join("0x%x\n" % va for va in vas)
+    cmd = _demand_write_cmd(vas)
+    if not cmd:
+        return
     try:
-        vexec("printf '%%s' '%s' >> /tmp/guest_want_vas.txt" % lines, 30)
+        vexec(cmd, 30)
     except Exception:
         pass
 
@@ -222,9 +240,9 @@ def _demand_loop():
         todo = [va for va, (f, l) in track.items() if now - l > 20.0]
         if not todo:
             continue
-        lines = "".join("0x%x\n" % va for va in todo)
+        cmd = _demand_write_cmd(todo)
         try:
-            vexec("printf '%%s' '%s' >> /tmp/guest_want_vas.txt" % lines, 30)
+            vexec(cmd, 30)
         except Exception:
             continue
         for va in todo: