tools: durable guest counter enumeration/injection and VA reader

The counter enumeration/injection workflow lived in the guest's /tmp and was
lost on every restart. Make it durable under tools/guest-diag:

- sem_counters.py: translate a process's per-channel u32 completion counters
  (16-byte stride in the /dev/nvidiactl counter page) to guest PAs through
  /proc/<pid>/pagemap; --pairs emits handle,va,pa triples.
- sem_slots.py: read/write the counter slots via /proc/<pid>/mem (fallback
  for the host counter publish).
- read_va.py: hex dump a process VA (UVM sysmem GPU VAs are usually valid
  CPU VAs in the owning process); --u32 for method streams.
- inject_counters.sh: host-side one-shot: push the tool, take the GR handles
  from the live chan_dump, enumerate, then register each counter with
  sema_counter and pin its VA with sema_map_add.
- push_guest_tools.sh: push the new tools after every VM start.
- launch_qemu_direct.sh: parameterized mdev UUID/paths instead of a stale
  hardcoded one; committed so it survives checkouts.

1 files changed, 90 insertions, 0 deletions

diff --git a/tools/guest-diag/sem_counters.py b/tools/guest-diag/sem_counters.py
new file mode 100755
index 0000000..66af258
--- /dev/null
+++ b/tools/guest-diag/sem_counters.py
@@ -0,0 +1,90 @@
+#!/usr/bin/env python3
+# sem_counters.py - enumerate a guest process's per-channel GPU completion
+# counters (the u32 slots the client polls to observe push completion).
+#
+# The counters live in one sysmem page mapped through /dev/nvidiactl (rw-s);
+# each channel owns a 16-byte-strided u32 in it (observed layout: 20 counters
+# at page offset 0xec0, one per GR channel). This translates the slots to
+# guest PAs through /proc/<pid>/pagemap so the host side can register them
+# with the sema_counter module parameter.
+#
+# Usage:
+#   sudo python3 sem_counters.py <pid> <page-va> [count] [stride]
+#   sudo python3 sem_counters.py <pid> <page-va> --pairs <h1,h2,...>
+#
+# --pairs zips the given channel handles with the counter indices in order
+# (ascending handle = ascending counter index, the observed layout) and
+# prints "<handle>,<va>,<pa>" lines: handle/pa for the sema_counter parameter,
+# va/pa for the sema_map_add pin so pushes releasing the counter resolve.
+#
+# Needs root in the guest (pagemap reads). Uses only os/sys.
+import os
+import sys
+
+
+def parse_args(argv):
+    pid = int(argv[0])
+    page_va = int(argv[1], 16)
+    count = 20
+    stride = 16
+    offset = 0xec0
+    handles = None
+    rest = argv[2:]
+    i = 0
+    while i < len(rest):
+        a = rest[i]
+        if a == '--pairs':
+            handles = [int(x, 16) for x in rest[i + 1].split(',') if x]
+            i += 2
+            continue
+        if a.startswith('--count='):
+            count = int(a.split('=', 1)[1], 0)
+        elif a.startswith('--stride='):
+            stride = int(a.split('=', 1)[1], 0)
+        elif a.startswith('--offset='):
+            offset = int(a.split('=', 1)[1], 0)
+        elif i == 0:
+            count = int(a, 0)
+        elif i == 1:
+            stride = int(a, 0)
+        i += 1
+    return pid, page_va, count, stride, offset, handles
+
+
+def main():
+    pid, page_va, count, stride, offset, handles = parse_args(sys.argv[1:])
+
+    fd = os.open('/proc/%d/pagemap' % pid, os.O_RDONLY)
+    try:
+        pas = []
+        for i in range(count):
+            va = page_va + offset + i * stride
+            os.lseek(fd, (va // 4096) * 8, 0)
+            e = int.from_bytes(os.read(fd, 8), 'little')
+            present = (e >> 63) & 1
+            pfn = e & ((1 << 55) - 1)
+            pa = (pfn << 12) | (va & 0xfff)
+            pas.append((va, present, pa))
+    finally:
+        os.close(fd)
+
+    if handles is not None:
+        if len(handles) != len(pas):
+            print('ERROR: %d handles but %d counters' %
+                  (len(handles), len(pas)), file=sys.stderr)
+            return 1
+        for h, (va, present, pa) in zip(handles, pas):
+            if not present:
+                print('ERROR: VA=0x%x not present for handle 0x%x' %
+                      (va, h), file=sys.stderr)
+                return 1
+            print('0x%x,0x%x,%d' % (h, va, pa))
+    else:
+        for i, (va, present, pa) in enumerate(pas):
+            print('idx=%d VA=0x%x present=%d PA=0x%x' %
+                  (i, va, present, pa))
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())