This script wraps other tests to check that HugeTLB statistics are
restored to what they were before the test was run.

Does not account HugeTLB statistics updated by other non-test
processes running in the background while the test is running.

Change-Id: I1d827656ef215fd85e368f4a3629f306e7f33f18
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 ...memfd_wrap_test_check_hugetlb_reporting.sh | 95 +++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100755 tools/testing/selftests/kvm/guest_memfd_wrap_test_check_hugetlb_reporting.sh

diff --git a/tools/testing/selftests/kvm/guest_memfd_wrap_test_check_hugetlb_reporting.sh b/tools/testing/selftests/kvm/guest_memfd_wrap_test_check_hugetlb_reporting.sh
new file mode 100755
index 000000000000..475ec5c4ce1b
--- /dev/null
+++ b/tools/testing/selftests/kvm/guest_memfd_wrap_test_check_hugetlb_reporting.sh
@@ -0,0 +1,95 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Wrapper that runs test, checking that HugeTLB-related statistics have not
+# changed before and after test.
+#
+# Example:
+#   ./guest_memfd_wrap_test_check_hugetlb_reporting.sh ./guest_memfd_test
+#
+# Example of combining this with ./guest_memfd_provide_hugetlb_cgroup_mount.sh:
+#   ./guest_memfd_provide_hugetlb_cgroup_mount.sh \
+#     ./guest_memfd_wrap_test_check_hugetlb_reporting.sh \
+#     ./guest_memfd_hugetlb_reporting_test
+#
+# Copyright (C) 2025, Google LLC.
+
+declare -A baseline
+
+hugetlb_sizes=(
+  "2048kB"
+  "1048576kB"
+)
+
+statistics=(
+  "free_hugepages"
+  "nr_hugepages"
+  "nr_overcommit_hugepages"
+  "resv_hugepages"
+  "surplus_hugepages"
+)
+
+cgroup_hugetlb_sizes=(
+  "2MB"
+  "1GB"
+)
+
+cgroup_statistics=(
+  "limit_in_bytes"
+  "max_usage_in_bytes"
+  "usage_in_bytes"
+)
+
+establish_statistics_baseline() {
+  for size in "${hugetlb_sizes[@]}"; do
+
+    for statistic in "${statistics[@]}"; do
+
+      local path="/sys/kernel/mm/hugepages/hugepages-${size}/${statistic}"
+      baseline["$path"]=$(cat "$path")
+
+    done
+
+  done
+
+  if [ -n "$HUGETLB_CGROUP_PATH" ]; then
+
+    for size in "${cgroup_hugetlb_sizes[@]}"; do
+
+      for statistic in "${cgroup_statistics[@]}"; do
+
+        local rsvd_path="${HUGETLB_CGROUP_PATH}/hugetlb.${size}.rsvd.${statistic}"
+        local path="${HUGETLB_CGROUP_PATH}/hugetlb.${size}.${statistic}"
+
+        baseline["$rsvd_path"]=$(cat "$rsvd_path")
+        baseline["$path"]=$(cat "$path")
+
+      done
+
+    done
+
+  fi
+}
+
+assert_path_at_baseline() {
+  local path=$1
+
+  current=$(cat "$path")
+  expected=${baseline["$path"]}
+  if [ "$current" != "$expected"  ]; then
+    echo "$path was $current instead of $expected"
+  fi
+}
+
+assert_statistics_at_baseline() {
+  for path in "${!baseline[@]}"; do
+    assert_path_at_baseline $path
+  done
+}
+
+
+establish_statistics_baseline
+
+$@
+
+assert_statistics_at_baseline
-- 
2.49.0.1045.g170613ef41-goog