[PATCH v5] selftests/vm: Only run 128TBswitch with 5-level paging

[Adam Sindelar <adam@wowsignal.io>]

The test va_128TBswitch.c expects to be able to pass mmap an address hint
and length that cross the address 1<<47. On x86_64, this is not possible
without 5-level page tables, so the test fails.

The test is already only run on 64-bit powerpc and x86_64 archs, but this
patch adds an additional check on x86_64 that skips the test if PG_TABLE_LEVELS
< 5.  There is precedent for checking /proc/config.gz in selftests, e.g. in
selftests/firmware.

Running the tests produces the desired output:

sudo make -C tools/testing/selftests TARGETS=vm run_tests
---------------------------
running ./va_128TBswitch.sh
---------------------------
./va_128TBswitch.sh: PG_TABLE_LEVELS=4, must be >= 5 to run this test
[SKIP]
-------------------------------

Signed-off-by: Adam Sindelar <adam@wowsignal.io>
---
V4 -> V5: Renamed "die" to "fail" (missed the review comment, sorry!)
V3 -> V4: Restrict the check to x86_64
V2 -> V3: Clean up the commit message
V1 -> V2: Variables local, fixed Makefile typo, comment on gzip usage

 tools/testing/selftests/vm/Makefile          |  1 +
 tools/testing/selftests/vm/run_vmtests.sh    |  2 +-
 tools/testing/selftests/vm/va_128TBswitch.sh | 54 ++++++++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100755 tools/testing/selftests/vm/va_128TBswitch.sh

diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index 44f25acfbeca..6a34209379a4 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -93,6 +93,7 @@ TEST_PROGS := run_vmtests.sh
 
 TEST_FILES := test_vmalloc.sh
 TEST_FILES += test_hmm.sh
+TEST_FILES += va_128TBswitch.sh
 
 KSFT_KHDR_INSTALL := 1
 include ../lib.mk
diff --git a/tools/testing/selftests/vm/run_vmtests.sh b/tools/testing/selftests/vm/run_vmtests.sh
index 41fce8bea929..27c01c35c7a9 100755
--- a/tools/testing/selftests/vm/run_vmtests.sh
+++ b/tools/testing/selftests/vm/run_vmtests.sh
@@ -151,7 +151,7 @@ if [ $VADDR64 -ne 0 ]; then
 	run_test ./virtual_address_range
 
 	# virtual address 128TB switch test
-	run_test ./va_128TBswitch
+	run_test ./va_128TBswitch.sh
 fi # VADDR64
 
 # vmalloc stability smoke test
diff --git a/tools/testing/selftests/vm/va_128TBswitch.sh b/tools/testing/selftests/vm/va_128TBswitch.sh
new file mode 100755
index 000000000000..334d12715ac3
--- /dev/null
+++ b/tools/testing/selftests/vm/va_128TBswitch.sh
@@ -0,0 +1,54 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (C) 2022 Adam Sindelar (Meta) <adam@wowsignal.io>
+#
+# This is a test for mmap behavior with 5-level paging. This script wraps the
+# real test to check that the kernel is configured to support at least 5
+# pagetable levels.
+
+# 1 means the test failed
+exitcode=1
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+fail()
+{
+    echo "$1"
+    exit $exitcode
+}
+
+check_supported_x86_64()
+{
+    local config="/proc/config.gz"
+    [[ -f "${config}" ]] || config="/boot/config-$(uname -r)"
+    [[ -f "${config}" ]] || fail "Cannot find kernel config in /proc or /boot"
+
+    # gzip -dcfq automatically handles both compressed and plaintext input.
+    # See man 1 gzip under '-f'.
+    local pg_table_levels=$(gzip -dcfq "${config}" | grep PGTABLE_LEVELS | cut -d'=' -f 2)
+
+    if [[ "${pg_table_levels}" -lt 5 ]]; then
+        echo "$0: PGTABLE_LEVELS=${pg_table_levels}, must be >= 5 to run this test"
+        exit $ksft_skip
+    fi
+}
+
+check_test_requirements()
+{
+    # The test supports x86_64 and powerpc64. We currently have no useful
+    # eligibility check for powerpc64, and the test itself will reject other
+    # architectures.
+    case `uname -m` in
+        "x86_64")
+            check_supported_x86_64
+        ;;
+        *)
+            return 0
+        ;;
+    esac
+}
+
+check_test_requirements
+./va_128TBswitch
-- 
2.35.1