linux-kernel - [PATCH bpf-next] powerpc/bpf: Fix warning for unused ori31

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Message-ID: <20250619142647.2157017-1-luis.gerhorst@fau.de>
Date: Thu, 19 Jun 2025 16:26:47 +0200
From: Luis Gerhorst <luis.gerhorst@....de>
To: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Hari Bathini <hbathini@...ux.ibm.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Naveen N Rao <naveen@...nel.org>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Luis Gerhorst <luis.gerhorst@....de>,
	bpf@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org
Cc: kernel test robot <lkp@...el.com>
Subject: [PATCH bpf-next] powerpc/bpf: Fix warning for unused ori31_emitted

Without this, the compiler (clang21) might emit a warning under W=1
because the variable ori31_emitted is set but never used if
CONFIG_PPC_BOOK3S_64=n.

Without this patch:

$ make -j $(nproc) W=1 ARCH=powerpc SHELL=/bin/bash arch/powerpc/net
  [...]
  CC      arch/powerpc/net/bpf_jit_comp.o
  CC      arch/powerpc/net/bpf_jit_comp64.o
../arch/powerpc/net/bpf_jit_comp64.c: In function 'bpf_jit_build_body':
../arch/powerpc/net/bpf_jit_comp64.c:417:28: warning: variable 'ori31_emitted' set but not used [-Wunused-but-set-variable]
  417 |         bool sync_emitted, ori31_emitted;
      |                            ^~~~~~~~~~~~~
  AR      arch/powerpc/net/built-in.a

With this patch:

  [...]
  CC      arch/powerpc/net/bpf_jit_comp.o
  CC      arch/powerpc/net/bpf_jit_comp64.o
  AR      arch/powerpc/net/built-in.a

Fixes: dff883d9e93a ("bpf, arm64, powerpc: Change nospec to include v1 barrier")
Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202506180402.uUXwVoSH-lkp@intel.com/
Signed-off-by: Luis Gerhorst <luis.gerhorst@....de>
---
 arch/powerpc/net/bpf_jit_comp64.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index 3665ff8bb4bc..a25a6ffe7d7c 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -820,13 +820,12 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
 		case BPF_ST | BPF_NOSPEC:
 			sync_emitted = false;
 			ori31_emitted = false;
-#ifdef CONFIG_PPC_E500
-			if (!bpf_jit_bypass_spec_v1()) {
+			if (IS_ENABLED(CONFIG_PPC_E500) &&
+			    !bpf_jit_bypass_spec_v1()) {
 				EMIT(PPC_RAW_ISYNC());
 				EMIT(PPC_RAW_SYNC());
 				sync_emitted = true;
 			}
-#endif
 			if (!bpf_jit_bypass_spec_v4()) {
 				switch (stf_barrier) {
 				case STF_BARRIER_EIEIO:
@@ -849,10 +848,10 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
 					break;
 				}
 			}
-#ifdef CONFIG_PPC_BOOK3S_64
-			if (!bpf_jit_bypass_spec_v1() && !ori31_emitted)
+			if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) &&
+			    !bpf_jit_bypass_spec_v1() &&
+			    !ori31_emitted)
 				EMIT(PPC_RAW_ORI(_R31, _R31, 0));
-#endif
 			break;
 
 		/*

base-commit: cd7312a78f36e981939abe1cd1f21d355e083dfe
-- 
2.49.0