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 D6587239E8B for ; Tue, 22 Jul 2025 09:34:47 +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=1753176891; cv=none; b=fwWYPTx3FbWYdVZT1EAWFzDm5CAXGKPpS8aJ3bxHOL7aEfNTps2/Xbu4VcidnzxoYBb7SDciyQjHXW8k06eLTXtu2JEOeND9sJjh59UBlsrTQnomUmM3oSY+8GjE0Gp+dG3+y2hAqCdTPM8NL0fTk31PEam3TSU62ml+lQXg9Us= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753176891; c=relaxed/simple; bh=iFKePA9680XzRjV70hdBXc62Hpz8lkQ7fU85KVFrFy0=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=ldO3wn+mVlxsSe1gtCjOmnRxSPJGvFsH5d1YgIUiWoJSc3Ul4xYGFxgldkGzakkumSQiX1AHT2Xc/HKnDJckP+Nz4NVR156P6ehxrgLgR6CmwJEP6gb+YoDJpmC1aB4GQ2BeOf564bsxpthV6T4/pEGuM4QIo2ROzvKCN8SAhao= 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: 18955a6066df11f0b29709d653e92f7d-20250722 X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.45,REQID:1e3a7a24-7a6d-406e-a4ea-fac57fd3d0f4,IP:10, URL:0,TC:0,Content:-5,EDM:0,RT:0,SF:-40,FILE:0,BULK:0,RULE:Release_Ham,ACT ION:release,TS:-35 X-CID-INFO: VERSION:1.1.45,REQID:1e3a7a24-7a6d-406e-a4ea-fac57fd3d0f4,IP:10,UR L:0,TC:0,Content:-5,EDM:0,RT:0,SF:-40,FILE:0,BULK:0,RULE:Release_Ham,ACTIO N:release,TS:-35 X-CID-META: VersionHash:6493067,CLOUDID:b991f3ddc67df1f5aacca9efeaa9fb13,BulkI D:250722173443WLR6NJDC,BulkQuantity:0,Recheck:0,SF:10|24|44|64|66|78|80|81 |82|83|102|841,TC:nil,Content:0|51,EDM:-3,IP:-2,URL:0,File:nil,RT:nil,Bulk :nil,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0,LES:1,SPR:NO,DKR:0,DKP:0,BRR:0, BRE:0,ARC:0 X-CID-BVR: 0 X-CID-BAS: 0,_,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR,TF_CID_SPAM_FSI X-UUID: 18955a6066df11f0b29709d653e92f7d-20250722 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 733763614; Tue, 22 Jul 2025 17:34:42 +0800 Message-ID: <4443b6e55d74fd2b78e6790b0719b32e70a0df00.camel@kylinos.cn> Subject: =?gb2312?Q?re=A3=BA=5BPATCH?= v2 1/2] 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, kernel@xen0n.name, chenhuacai@kernel.org, yangtiezhu@loongson.cn, jolsa@kernel.org, haoluo@google.com, 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, ast@kernel.org Date: Tue, 22 Jul 2025 17:34:37 +0800 In-Reply-To: References: <20250708071840.556686-1-jianghaoran@kylinos.cn> <20250708071840.556686-2-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: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 在 2025-07-16星期三的 09:31 +0800，Hengqi Chen写道： > Hi Haoran, > > On Tue, Jul 8, 2025 at 3:19 PM Haoran Jiang < jianghaoran@kylinos.cn> > wrote: > > > > The extra pass of bpf_int_jit_compile() skips JIT context initialization > > which essentially skips offset calculation leaving 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. > > > > "does not meet expectations" ? Simply "is wrong" ? > > The subject line should be something like: > Fix jump offset calculation in tailcall > > It's a fix, not optimization. > > Other than that, feel free to add: > Reviewed-by: Hengqi Chen < hengqi.chen@gmail.com> > I will make the modification in the next version. > > 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] > > > > Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support") > > Signed-off-by: Haoran Jiang < > > jianghaoran@kylinos.cn > > > > > --- > > arch/loongarch/net/bpf_jit.c | 21 ++++++--------------- > > 1 file changed, 6 insertions(+), 15 deletions(-) > > > > diff --git a/arch/loongarch/net/bpf_jit.c > > b/arch/loongarch/net/bpf_jit.c > > index fa1500d4aa3e..5061bfc978f2 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(struct jit_ctx *ctx, int insn) > > { > > int off; > > u8 tcc = tail_call_reg(ctx); > > @@ -220,9 +218,10 @@ 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; > > + int tc_ninsn = 0; > > > > #define cur_offset (ctx->idx - idx0) > > -#define jmp_offset (out_offset - (cur_offset)) > > +#define jmp_offset (tc_ninsn - (cur_offset)) > > > > /* > > * a0: &ctx > > @@ -232,6 +231,8 @@ 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); > > /* bgeu $a2, $t1, jmp_offset */ > > @@ -263,15 +264,6 @@ 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: > > @@ -916,7 +908,7 @@ 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(ctx, i) < 0) > > return -EINVAL; > > break; > > > > @@ -1342,7 +1334,6 @@ 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 > > > >