From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1E7A8C433F5 for ; Tue, 19 Apr 2022 16:20:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232936AbiDSQW7 (ORCPT ); Tue, 19 Apr 2022 12:22:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32826 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244793AbiDSQW6 (ORCPT ); Tue, 19 Apr 2022 12:22:58 -0400 Received: from mail-pl1-x62d.google.com (mail-pl1-x62d.google.com [IPv6:2607:f8b0:4864:20::62d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DB3AF1ADB7; Tue, 19 Apr 2022 09:20:14 -0700 (PDT) Received: by mail-pl1-x62d.google.com with SMTP id be5so16210211plb.13; Tue, 19 Apr 2022 09:20:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=OpmsPVuh5gD407HNflz5sTTKTm92evyJFyu/dYazDZo=; b=pnQqoPHJCVZ7osuaM6ziIdZpm2hz+AabFwJ8YK6FroHsyTh4vi04iu04G7U6YX3lDx z7NSvoIzKwHnnpG511hZ5rEuR4SVcfoz91moRNElfykbxxif/HnGbL8MeV7L8y/6bo1Q AwPD2DtyNeVHeYSH/q5mEy/lDtjo2+1TV16H9TmHWPEuXn4WlPz7ueam7dqIA18U5WqZ QJr/80nWRD/jOjMvaWbJG+kthBP2La19NIevGNgZlsPeRQs8zy6KI8fCOE9YWSQ9LQWt nivh0z2dcmoS7RHgPXBT9f4weoKQ2pL+c/JBfH2RLtG88axkMatwhiQAHuvEJK9olS1g fM9w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=OpmsPVuh5gD407HNflz5sTTKTm92evyJFyu/dYazDZo=; b=MNjQCQBGUWCRuHB+v8mLNqCGXgOaw7wYYB1ZjBBhSF8sL8E30y6ri9lmCMXT+o9cUv lGpsdwIHnUYv5y5HY0DCp/5tf0WIiTN4VBYC4tt+rou/OrxgWL61LKNn8iUPldyzMcQe Di/Oad/2SYy1U8nnp67sBkH7qxMMIQHVBm8JDBAjU9b2Q2W9UXa919HKtOojYQhUbWrA e4a04b/pJL3OHazzBKstyKUCsSqx3fFA7zbSN4fwB1zVslXJiF0akfhO8k2D4rITbQVs YmJ/Hy+qindA3ZErVe4+M+66Oq+SZhj5q8GKs0jFqIBccvz5GettPh0KU+SN5Etb/3bK wolQ== X-Gm-Message-State: AOAM530Im/JScNprNw+9QjTygc6UH+5S6ENriRdF6yep2qS4YHE5pwZ0 4nRrs2/lDPVeoM2jrUyFVAGeOai7cpkZKFgspWg= X-Google-Smtp-Source: ABdhPJyXucgwjBUCNws7QdnR9RRUpd2+6dEbAAmKY2yrSY46/uXzNb3Tc8/z20cflB5jonVCuA1plDQ5pepJtZr+yYs= X-Received: by 2002:a17:903:2d1:b0:156:7ceb:b56f with SMTP id s17-20020a17090302d100b001567cebb56fmr16493322plk.11.1650385214168; Tue, 19 Apr 2022 09:20:14 -0700 (PDT) MIME-Version: 1.0 References: <20220414161233.170780-1-sdf@google.com> In-Reply-To: From: Alexei Starovoitov Date: Tue, 19 Apr 2022 09:20:03 -0700 Message-ID: Subject: Re: [PATCH bpf-next v2] bpf: move rcu lock management out of BPF_PROG_RUN routines To: Stanislav Fomichev Cc: Network Development , bpf , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Apr 19, 2022 at 8:42 AM wrote: > > On 04/18, Alexei Starovoitov wrote: > > On Mon, Apr 18, 2022 at 9:50 AM wrote: > > > > > > On 04/16, Alexei Starovoitov wrote: > > > > On Thu, Apr 14, 2022 at 9:12 AM Stanislav Fomichev > > wrote: > > > > > +static int > > > > > +bpf_prog_run_array_cg_flags(const struct cgroup_bpf *cgrp, > > > > > + enum cgroup_bpf_attach_type atype, > > > > > + const void *ctx, bpf_prog_run_fn > > run_prog, > > > > > + int retval, u32 *ret_flags) > > > > > +{ > > > > > + const struct bpf_prog_array_item *item; > > > > > + const struct bpf_prog *prog; > > > > > + const struct bpf_prog_array *array; > > > > > + struct bpf_run_ctx *old_run_ctx; > > > > > + struct bpf_cg_run_ctx run_ctx; > > > > > + u32 func_ret; > > > > > + > > > > > + run_ctx.retval = retval; > > > > > + migrate_disable(); > > > > > + rcu_read_lock(); > > > > > + array = rcu_dereference(cgrp->effective[atype]); > > > > > + item = &array->items[0]; > > > > > + old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx); > > > > > + while ((prog = READ_ONCE(item->prog))) { > > > > > + run_ctx.prog_item = item; > > > > > + func_ret = run_prog(prog, ctx); > > > > ... > > > > > + ret = bpf_prog_run_array_cg(&cgrp->bpf, CGROUP_GETSOCKOPT, > > > > > &ctx, bpf_prog_run, retval); > > > > > > > Did you check the asm that bpf_prog_run gets inlined > > > > after being passed as a pointer to a function? > > > > Crossing fingers... I suspect not every compiler can do that :( > > > > De-virtualization optimization used to be tricky. > > > > > > No, I didn't, but looking at it right now, both gcc and clang > > > seem to be doing inlining all way up to bpf_dispatcher_nop_func. > > > > > > clang: > > > > > > 0000000000001750 <__cgroup_bpf_run_filter_sock_addr>: > > > __cgroup_bpf_run_filter_sock_addr(): > > > ./kernel/bpf/cgroup.c:1226 > > > int __cgroup_bpf_run_filter_sock_addr(struct sock *sk, > > > struct sockaddr *uaddr, > > > enum cgroup_bpf_attach_type atype, > > > void *t_ctx, > > > u32 *flags) > > > { > > > > > > ... > > > > > > ./include/linux/filter.h:628 > > > ret = dfunc(ctx, prog->insnsi, prog->bpf_func); > > > 1980: 49 8d 75 48 lea 0x48(%r13),%rsi > > > bpf_dispatcher_nop_func(): > > > ./include/linux/bpf.h:804 > > > return bpf_func(ctx, insnsi); > > > 1984: 4c 89 f7 mov %r14,%rdi > > > 1987: 41 ff 55 30 call *0x30(%r13) > > > 198b: 89 c3 mov %eax,%ebx > > > > > > gcc (w/retpoline): > > > > > > 0000000000001110 <__cgroup_bpf_run_filter_sock_addr>: > > > __cgroup_bpf_run_filter_sock_addr(): > > > kernel/bpf/cgroup.c:1226 > > > { > > > > > > ... > > > > > > ./include/linux/filter.h:628 > > > ret = dfunc(ctx, prog->insnsi, prog->bpf_func); > > > 11c5: 49 8d 75 48 lea 0x48(%r13),%rsi > > > bpf_dispatcher_nop_func(): > > > ./include/linux/bpf.h:804 > > > 11c9: 48 8d 7c 24 10 lea 0x10(%rsp),%rdi > > > 11ce: e8 00 00 00 00 call 11d3 > > > <__cgroup_bpf_run_filter_sock_addr+0xc3> > > > 11cf: R_X86_64_PLT32 > > __x86_indirect_thunk_rax-0x4 > > > 11d3: 89 c3 mov %eax,%ebx > > > Hmm. I'm not sure how you've got this asm. > > Here is what I see with gcc 8 and gcc 10: > > bpf_prog_run_array_cg: > > ... > > movq %rcx, %r12 # run_prog, run_prog > > ... > > # ../kernel/bpf/cgroup.c:77: run_ctx.prog_item = item; > > movq %rbx, (%rsp) # item, run_ctx.prog_item > > # ../kernel/bpf/cgroup.c:78: if (!run_prog(prog, ctx) && > > !IS_ERR_VALUE((long)run_ctx.retval)) > > movq %rbp, %rsi # ctx, > > call *%r12 # run_prog > > > __cgroup_bpf_run_filter_sk: > > movq $bpf_prog_run, %rcx #, > > # ../kernel/bpf/cgroup.c:1202: return > > bpf_prog_run_array_cg(&cgrp->bpf, atype, sk, bpf_prog_run, 0); > > leaq 1520(%rax), %rdi #, tmp92 > > # ../kernel/bpf/cgroup.c:1202: return > > bpf_prog_run_array_cg(&cgrp->bpf, atype, sk, bpf_prog_run, 0); > > jmp bpf_prog_run_array_cg # > > > This is without kasan, lockdep and all debug configs are off. > > > So the generated code is pretty bad as I predicted :( > > > So I'm afraid this approach is no go. > > I've retested again and it still unrolls it for me on gcc 11 :-/ > Anyway, I guess we have two options: > > 1. Go back to defines. > 2. Don't pass a ptr to func, but pass an enum which indicates whether > to use bpf_prog_run or __bpf_prog_run_save_cb. Seems like in this > case the compiler shouldn't have any trouble unwrapping it? > > I'll prototype and send (2). If it won't work out we can always get back > to (1). Going back to defines is probably not necessary. Could you try moving bpf_prog_run_array_cg*() back to .h and use static __always_inline ?