[PATCH bpf-next v2 17/18] selftests/bpf: Clarify llvm dependency with possible selftest failures

[Yonghong Song <yhs@fb.com>]

Certain subtests in selftests core_reloc and core_reloc_btfgen
requires llvm ENUM64 support in llvm15. If an older compiler
is used, these subtests will fail. Make this requirement clear
in selftests README.rst file.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 tools/testing/selftests/bpf/README.rst | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/tools/testing/selftests/bpf/README.rst b/tools/testing/selftests/bpf/README.rst
index eb1b7541f39d..a83d78a58014 100644
--- a/tools/testing/selftests/bpf/README.rst
+++ b/tools/testing/selftests/bpf/README.rst
@@ -266,3 +266,21 @@ from running test_progs will look like:
   test_xdpwall:FAIL:Does LLVM have https://reviews.llvm.org/D109073? unexpected error: -4007
 
 __ https://reviews.llvm.org/D109073
+
+ENUM64 support and Clang version
+================================
+
+There are a few selftests requiring LLVM ENUM64 support. The LLVM ENUM64 is
+introduced in `Clang 15` [0_]. Without proper compiler support, the following selftests
+will fail:
+
+.. code-block:: console
+
+  #45 /73    core_reloc/enum64val:FAIL
+  #45 /74    core_reloc/enum64val___diff:FAIL
+  #45 /75    core_reloc/enum64val___val3_missing:FAIL
+  #46 /73    core_reloc_btfgen/enum64val:FAIL
+  #46 /74    core_reloc_btfgen/enum64val___diff:FAIL
+  #46 /75    core_reloc_btfgen/enum64val___val3_missing:FAIL
+
+.. _0: https://reviews.llvm.org/D124641
-- 
2.30.2