linux-kernel - [PATCH] powerpc/bpf: Only update ldimm64 during extra pass when it is an address

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Date:   Thu, 24 Nov 2022 09:39:38 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        bpf@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>
Subject: [PATCH] powerpc/bpf: Only update ldimm64 during extra pass when it is an address

ldimm64 is not only used for loading function addresses, and
the NOPs added for padding are impacting performance, so avoid
them when not necessary.

On QEMU mac99, with the patch:

test_bpf: #829 ALU64_MOV_K: all immediate value magnitudes jited:1 167436810 PASS
test_bpf: #831 ALU64_OR_K: all immediate value magnitudes jited:1 170702940 PASS

Without the patch:

test_bpf: #829 ALU64_MOV_K: all immediate value magnitudes jited:1 173012360 PASS
test_bpf: #831 ALU64_OR_K: all immediate value magnitudes jited:1 176424090 PASS

That's a 3.5% performance improvement.

Fixes: f9320c49993c ("powerpc/bpf: Update ldimm64 instructions during extra pass")
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/net/bpf_jit_comp.c   | 3 ++-
 arch/powerpc/net/bpf_jit_comp32.c | 5 +++--
 arch/powerpc/net/bpf_jit_comp64.c | 5 +++--
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 43e634126514..206b698723a3 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -68,7 +68,8 @@ static int bpf_jit_fixup_addresses(struct bpf_prog *fp, u32 *image,
 			 * of the JITed sequence remains unchanged.
 			 */
 			ctx->idx = tmp_idx;
-		} else if (insn[i].code == (BPF_LD | BPF_IMM | BPF_DW)) {
+		} else if (insn[i].code == (BPF_LD | BPF_IMM | BPF_DW) &&
+			   insn[i].src_reg == BPF_PSEUDO_FUNC) {
 			tmp_idx = ctx->idx;
 			ctx->idx = addrs[i] / 4;
 #ifdef CONFIG_PPC32
diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
index a379b0ce19ff..878f8a88d83e 100644
--- a/arch/powerpc/net/bpf_jit_comp32.c
+++ b/arch/powerpc/net/bpf_jit_comp32.c
@@ -960,8 +960,9 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
 			PPC_LI32(dst_reg_h, (u32)insn[i + 1].imm);
 			PPC_LI32(dst_reg, (u32)insn[i].imm);
 			/* padding to allow full 4 instructions for later patching */
-			for (j = ctx->idx - tmp_idx; j < 4; j++)
-				EMIT(PPC_RAW_NOP());
+			if (insn[i].src_reg == BPF_PSEUDO_FUNC)
+				for (j = ctx->idx - tmp_idx; j < 4; j++)
+					EMIT(PPC_RAW_NOP());
 			/* Adjust for two bpf instructions */
 			addrs[++i] = ctx->idx * 4;
 			break;
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index 29ee306d6302..af8bdb5553cd 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -938,8 +938,9 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
 			tmp_idx = ctx->idx;
 			PPC_LI64(dst_reg, imm64);
 			/* padding to allow full 5 instructions for later patching */
-			for (j = ctx->idx - tmp_idx; j < 5; j++)
-				EMIT(PPC_RAW_NOP());
+			if (insn[i].src_reg == BPF_PSEUDO_FUNC)
+				for (j = ctx->idx - tmp_idx; j < 5; j++)
+					EMIT(PPC_RAW_NOP());
 			/* Adjust for two bpf instructions */
 			addrs[++i] = ctx->idx * 4;
 			break;
-- 
2.38.1