docs/bpf: Default cpu version changed from v1 to v3 in llvm 20
The default cpu version is changed from v1 to v3 in llvm version 20.
See [1] for more detailed reasoning. Update bpf_devel_QA.rst so
developers can find such information easily.
[1] https://github.com/llvm/llvm-project/pull/107008
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20250612043049.2411989-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
diff --git a/Documentation/bpf/bpf_devel_QA.rst b/Documentation/bpf/bpf_devel_QA.rst
index 0acb4c9..45bc5c5 100644
--- a/Documentation/bpf/bpf_devel_QA.rst
+++ b/Documentation/bpf/bpf_devel_QA.rst
@@ -611,9 +611,10 @@
it into LLVM?
A: LLVM has a ``-mcpu`` selector for the BPF back end in order to allow
-the selection of BPF instruction set extensions. By default the
-``generic`` processor target is used, which is the base instruction set
-(v1) of BPF.
+the selection of BPF instruction set extensions. Before llvm version 20,
+the ``generic`` processor target is used, which is the base instruction
+set (v1) of BPF. Since llvm 20, the default processor target has changed
+to instruction set v3.
LLVM has an option to select ``-mcpu=probe`` where it will probe the host
kernel for supported BPF instruction set extensions and selects the
