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 EEF6C1494A9; Thu, 26 Jun 2025 01:34:30 +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=1750901673; cv=none; b=N7ePKYoAuRyV/SAWoX0l82+CiMI04PJ0EV3ryItejQjMA7WSPnjbTAzD/Y5dCL03VQkpeQmJfFGnxu7h9yJ9OzMNBeKw0cXLoEi7sYt1d1dTfN8Wp5Ja0GvsVREdXdbJXTsBRUOS/BY3XPwV1BdfD1Mgs6HX6oGLQXMusam0wHs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750901673; c=relaxed/simple; bh=Sze5LiyiLLQnYq4jp6G/3KXHUq2Jer/dJECFnSftYaE=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=VyE2AHmTal3SdLNB3qvA4SmCMpDbYsg9T3lNqw1sRvkbBIRhcqIjOfiSqmoBB8CbFvX+j6zpiDLwLtPLu5ts38ubVlsLwMx2HJ39PkmSBUmDd1ibOpxqTEHQy4C344IQr8wlo2EAs2RXHIUI0+Hv4V5UYLo7np1rUURMQxucHr8= 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: b1520684522d11f0b29709d653e92f7d-20250626 X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.45,REQID:b8690f9c-930e-4fdf-a37f-3d48761e6797,IP:10, URL:0,TC:0,Content:0,EDM:0,RT:0,SF:-15,FILE:0,BULK:0,RULE:Release_Ham,ACTI ON:release,TS:-5 X-CID-INFO: VERSION:1.1.45,REQID:b8690f9c-930e-4fdf-a37f-3d48761e6797,IP:10,UR L:0,TC:0,Content:0,EDM:0,RT:0,SF:-15,FILE:0,BULK:0,RULE:Release_Ham,ACTION :release,TS:-5 X-CID-META: VersionHash:6493067,CLOUDID:0f9cb000345e11a0c4ca7a113f1f1173,BulkI D:250626092039VEVI8ELM,BulkQuantity:3,Recheck:0,SF:17|19|24|44|64|66|78|80 |81|82|83|102|841,TC:nil,Content:0|51,EDM:-3,IP:-2,URL:99|1,File:nil,RT:ni l,Bulk:40,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0,LES:1,SPR:NO,DKR:0,DKP:0,B RR:0,BRE:0,ARC:0 X-CID-BVR: 0,NGT X-CID-BAS: 0,NGT,0,_ X-CID-FACTOR: TF_CID_SPAM_FSD,TF_CID_SPAM_FSI,TF_CID_SPAM_ULS,TF_CID_SPAM_SNR, TF_CID_SPAM_FAS X-UUID: b1520684522d11f0b29709d653e92f7d-20250626 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 1659417453; Thu, 26 Jun 2025 09:34:25 +0800 Message-ID: <078ba5da7510db3c7eca281c417cdf49cfa26f07.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: Huacai Chen Cc: Hengqi Chen , loongarch@lists.linux.dev, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@xen0n.name, 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: Thu, 26 Jun 2025 09:34:11 +0800 In-Reply-To: References: <20250528104032.1237415-1-jianghaoran@kylinos.cn> <68ec5a7f3cc63dc19397b3ce0649716e0fac8d49.camel@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 2025-06-24星期二的 20:09 +0800，Huacai Chen写道： > Hi, Haoran, > > On Fri, May 30, 2025 at 9:22 AM jianghaoran < > jianghaoran@kylinos.cn > > wrote: > > > > > > > > > > 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. > > Do you mean you will update this patch? > > Huacai > yes, I'm making revisions according to the suggestions. > > > > > > > [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 > > > > > > > >