From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailgw.kylinos.cn (mailgw.kylinos.cn [124.126.103.232]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9C7C078F59; Fri, 30 May 2025 01:22:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=124.126.103.232 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748568133; cv=none; b=GvcoEKWzIkdnVmwAPUcYw3/ioxJQEnGi3ppzvLf/DXY24V3WA1R3vhbG37DSCFor7dGDGwoza9Y55HjHt1TYGUMBCqpvwA+co4XouocNlriTvBL7Av/uf+XhWGdRHycsgPZO/1vUmYdXKxRrpc7n4bB+RYp33XrudMywnTEKc5o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748568133; c=relaxed/simple; bh=cPZgUdjIWra0PdLQpoq1G4ikubdy55BGyBeN7H0ghQc=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=NGgcm+Y/UsTtcoj0zO+tDRD8PDK3hGT51wfgeT9CBNrF+orZf6rWJjIQG7d9y80g94Us0XbGjjE5I4pO0Arrq8d6Cyp+soi4z6s+gqMEJCncPyEDOZi9MihQWqRtkXxBkL4khyrK3ckCFlzq+CoSLpgFzOdLh3Tk1nnJMjxaQ2E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn; spf=pass smtp.mailfrom=kylinos.cn; arc=none smtp.client-ip=124.126.103.232 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kylinos.cn X-UUID: 7aeb099a3cf411f0b29709d653e92f7d-20250530 X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.45,REQID:61bc4a82-4730-41a2-ae0f-7d2ed25cec8c,IP:10, URL:0,TC:0,Content:0,EDM:0,RT:0,SF:-5,FILE:0,BULK:0,RULE:Release_Ham,ACTIO N:release,TS:5 X-CID-INFO: VERSION:1.1.45,REQID:61bc4a82-4730-41a2-ae0f-7d2ed25cec8c,IP:10,UR L:0,TC:0,Content:0,EDM:0,RT:0,SF:-5,FILE:0,BULK:0,RULE:Release_Ham,ACTION: release,TS:5 X-CID-META: VersionHash:6493067,CLOUDID:7101c88277929fe5165bb6c834cba4f3,BulkI D:250529133829GCJDP53I,BulkQuantity:1,Recheck:0,SF:17|19|24|43|64|66|74|78 |80|81|82|83|100|101|102|841,TC:nil,Content:0|51,EDM:-3,IP:-2,URL:99|1,Fil e:nil,RT:nil,Bulk:40,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0,LES:1,SPR:NO,DK R:0,DKP:0,BRR:0,BRE:0,ARC:0 X-CID-BVR: 0,NGT X-CID-BAS: 0,NGT,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR,TF_CID_SPAM_FAS,TF_CID_SPAM_FSD,TF_CID_SPAM_FSI, TF_CID_SPAM_ULS X-UUID: 7aeb099a3cf411f0b29709d653e92f7d-20250530 X-User: jianghaoran@kylinos.cn Received: from [192.168.31.67] [(223.70.159.239)] by mailgw.kylinos.cn (envelope-from ) (Generic MTA with TLSv1.3 TLS_AES_256_GCM_SHA384 256/256) with ESMTP id 1991867234; Fri, 30 May 2025 09:21:58 +0800 Message-ID: <68ec5a7f3cc63dc19397b3ce0649716e0fac8d49.camel@kylinos.cn> Subject: =?gb2312?Q?=BB=D8=B8=B4=A3=BA=5BPATCH=5D?= LoongArch: BPF: Optimize the calculation method of jmp_offset in the emit_bpf_tail_call function From: jianghaoran To: Hengqi Chen Cc: loongarch@lists.linux.dev, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@xen0n.name, chenhuacai@kernel.org, yangtiezhu@loongson.cn, haoluo@google.com, jolsa@kernel.org, sdf@fomichev.me, kpsingh@kernel.org, john.fastabend@gmail.com, yonghong.song@linux.dev, song@kernel.org, eddyz87@gmail.com, martin.lau@linux.dev, andrii@kernel.org, daniel@iogearbox.net Date: Fri, 30 May 2025 09:21:54 +0800 In-Reply-To: References: <20250528104032.1237415-1-jianghaoran@kylinos.cn> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.1-2kord0k2.4.25.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 在 2025-05-29星期四的 10:02 +0800，Hengqi Chen写道： > Hi Haoran, > > On Wed, May 28, 2025 at 6:40 PM Haoran Jiang < > jianghaoran@kylinos.cn > > wrote: > > For a ebpf subprog JIT，the last call bpf_int_jit_compile > > function will > > directly enter the skip_init_ctx process. At this point, > > out_offset = -1, > > the jmp_offset in emit_bpf_tail_call is calculated > > by #define jmp_offset (out_offset - (cur_offset)) is a negative > > number, > > which does not meet expectations.The final generated assembly > > as follow. > > > > 54: bgeu $a2, $t1, -8 # 0x0000004c > > 58: addi.d $a6, $s5, -1 > > 5c: bltz $a6, -16 # 0x0000004c > > 60: alsl.d $t2, $a2, $a1, 0x3 > > 64: ld.d $t2, $t2, 264 > > 68: beq $t2, $zero, -28 # 0x0000004c > > > > Before apply this patch, the follow test case will reveal soft > > lock issues. > > > > cd tools/testing/selftests/bpf/ > > ./test_progs --allow=tailcalls/tailcall_bpf2bpf_1 > > > > dmesg: > > watchdog: BUG: soft lockup - CPU#2 stuck for 26s! > > [test_progs:25056] > > > > This is a known issue. Does this change pass all tailcall tests ? > If not, please refer to the tailcall hierarchy patchset([1]). > We should address it once and for all. Thanks. > > [1]: > https://lore.kernel.org/bpf/20240714123902.32305-1-hffilwlqm@gmail.com/ > > Thanks,I'll keep looking into these patches. > > Signed-off-by: Haoran Jiang < > > jianghaoran@kylinos.cn > > > > > --- > > arch/loongarch/net/bpf_jit.c | 28 +++++++++------------------- > > 1 file changed, 9 insertions(+), 19 deletions(-) > > > > diff --git a/arch/loongarch/net/bpf_jit.c > > b/arch/loongarch/net/bpf_jit.c > > index fa1500d4aa3e..d85490e7de89 100644 > > --- a/arch/loongarch/net/bpf_jit.c > > +++ b/arch/loongarch/net/bpf_jit.c > > @@ -208,9 +208,7 @@ bool bpf_jit_supports_far_kfunc_call(void) > > return true; > > } > > > > -/* initialized on the first pass of build_body() */ > > -static int out_offset = -1; > > -static int emit_bpf_tail_call(struct jit_ctx *ctx) > > +static int emit_bpf_tail_call(int insn, struct jit_ctx *ctx) > > { > > int off; > > u8 tcc = tail_call_reg(ctx); > > @@ -220,9 +218,8 @@ static int emit_bpf_tail_call(struct > > jit_ctx *ctx) > > u8 t2 = LOONGARCH_GPR_T2; > > u8 t3 = LOONGARCH_GPR_T3; > > const int idx0 = ctx->idx; > > - > > -#define cur_offset (ctx->idx - idx0) > > -#define jmp_offset (out_offset - (cur_offset)) > > + int tc_ninsn = 0; > > + int jmp_offset = 0; > > > > /* > > * a0: &ctx > > @@ -232,8 +229,11 @@ static int emit_bpf_tail_call(struct > > jit_ctx *ctx) > > * if (index >= array->map.max_entries) > > * goto out; > > */ > > + tc_ninsn = insn ? ctx->offset[insn+1] - ctx- > > >offset[insn] : > > + ctx->offset[0]; > > off = offsetof(struct bpf_array, map.max_entries); > > emit_insn(ctx, ldwu, t1, a1, off); > > + jmp_offset = tc_ninsn - (ctx->idx - idx0); > > /* bgeu $a2, $t1, jmp_offset */ > > if (emit_tailcall_jmp(ctx, BPF_JGE, a2, t1, jmp_offset) > > < 0) > > goto toofar; > > @@ -243,6 +243,7 @@ static int emit_bpf_tail_call(struct > > jit_ctx *ctx) > > * goto out; > > */ > > emit_insn(ctx, addid, REG_TCC, tcc, -1); > > + jmp_offset = tc_ninsn - (ctx->idx - idx0); > > if (emit_tailcall_jmp(ctx, BPF_JSLT, REG_TCC, > > LOONGARCH_GPR_ZERO, jmp_offset) < 0) > > goto toofar; > > > > @@ -254,6 +255,7 @@ static int emit_bpf_tail_call(struct > > jit_ctx *ctx) > > emit_insn(ctx, alsld, t2, a2, a1, 2); > > off = offsetof(struct bpf_array, ptrs); > > emit_insn(ctx, ldd, t2, t2, off); > > + jmp_offset = tc_ninsn - (ctx->idx - idx0); > > /* beq $t2, $zero, jmp_offset */ > > if (emit_tailcall_jmp(ctx, BPF_JEQ, t2, > > LOONGARCH_GPR_ZERO, jmp_offset) < 0) > > goto toofar; > > @@ -263,22 +265,11 @@ static int emit_bpf_tail_call(struct > > jit_ctx *ctx) > > emit_insn(ctx, ldd, t3, t2, off); > > __build_epilogue(ctx, true); > > > > - /* out: */ > > - if (out_offset == -1) > > - out_offset = cur_offset; > > - if (cur_offset != out_offset) { > > - pr_err_once("tail_call out_offset = %d, > > expected %d!\n", > > - cur_offset, out_offset); > > - return -1; > > - } > > - > > return 0; > > > > toofar: > > pr_info_once("tail_call: jump too far\n"); > > return -1; > > -#undef cur_offset > > -#undef jmp_offset > > } > > > > static void emit_atomic(const struct bpf_insn *insn, struct > > jit_ctx *ctx) > > @@ -916,7 +907,7 @@ static int build_insn(const struct bpf_insn > > *insn, struct jit_ctx *ctx, bool ext > > /* tail call */ > > case BPF_JMP | BPF_TAIL_CALL: > > mark_tail_call(ctx); > > - if (emit_bpf_tail_call(ctx) < 0) > > + if (emit_bpf_tail_call(i, ctx) < 0) > > return -EINVAL; > > break; > > > > @@ -1342,7 +1333,6 @@ struct bpf_prog > > *bpf_int_jit_compile(struct bpf_prog *prog) > > if (tmp_blinded) > > bpf_jit_prog_release_other(prog, prog == > > orig_prog ? tmp : orig_prog); > > > > - out_offset = -1; > > > > return prog; > > > > -- > > 2.43.0 > >