vgsp-sema: re-arm ring/push-buffer discovery latches on channel registration; scanner streams anonymous high-VA buffers

Second-client wedge fix: a new GSP session re-registers the same channel
handles/ranks, but the per-rank one-shot ring/push-buffer discovery latches
stayed set from the previous session, so the new session's ring was never
re-autopinned (ring_auto=0 pb=0/0, nomap growing) and the guest spun in its
channel-creation wait. svc_chan_rearm_rank() clears the latches on every
channel registration; all post-fix cycles launch the second client.

Scanner: guest_pin_stream.py now streams the client's anonymous high-VA
mappings (cudaMalloc buffers were skipped by the old len(parts)<6 check),
so the host can learn their pages.

Diagnostics: PT-window lines, per-window first words, post-OK qmdwin
w48..59. Remaining: the fill-time svc_ipin_lookup miss for the second
client's a/b/c pins (they exist in the pin log but are not seen at fill
time) - next session.

1 files changed, 12 insertions, 3 deletions

diff --git a/tools/guest-diag/guest_pin_stream.py b/tools/guest-diag/guest_pin_stream.py
index 04aba73..739aeca 100644
--- a/tools/guest-diag/guest_pin_stream.py
+++ b/tools/guest-diag/guest_pin_stream.py
@@ -778,10 +778,19 @@ def scan_vmas(fd, pid, out):
     try:
         for line in maps:
             parts = line.split()
-            if len(parts) < 6:
+            if len(parts) < 5:
                 continue
-            path = parts[5]
-            if not any(p in path for p in VMA_PATHS):
+            # Anonymous mappings (no path field) are the client's UVM sysmem
+            # buffers when the driver maps them without a /dev/zero backing:
+            # the second client's cudaMalloc'd data buffers show up exactly
+            # like that (e.g. 75d7b0000000-75d7b0021000 rw-p 00000000 00:00 0)
+            # and were skipped by the old len<6 check, so their pages never
+            # reached the host and the forwarded launch could not resolve
+            # them (all-zero results for the second client). Accept them at
+            # the high-VA range; the VMA_LO bound and the pagemap present/PFN
+            # filters keep the set to real GPU mappings.
+            path = parts[5] if len(parts) >= 6 else ''
+            if path and not any(p in path for p in VMA_PATHS):
                 continue
             try:
                 a, b = parts[0].split('-')