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 B07F8C433EF for ; Mon, 18 Apr 2022 16:50:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346447AbiDRQx3 (ORCPT ); Mon, 18 Apr 2022 12:53:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55298 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232738AbiDRQx2 (ORCPT ); Mon, 18 Apr 2022 12:53:28 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CE5042C644 for ; Mon, 18 Apr 2022 09:50:48 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-2ec06f77db8so123760757b3.8 for ; Mon, 18 Apr 2022 09:50:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=Oyh1WpmZyRhAh6LbbmL6kVxO7rVD6ZzMLRjNqyG46HQ=; b=H5/ql9180csX6oJqirVWeYuzXUO+VYAqhiOVAKr130ZSZbia9k7REtHroXdJ//eT5f 2UTCgG7RsO29dh78OkUee9EDBGnTiBnbb7yAK6GiKTYJbcMaPe6Ewb27ap0Ha4HKAp80 lt99p5UqHzCzGZZAkf5x2Hdb84ul1212ICPYEUtzqyQ0F0haiUZkm+opjIv+EGTNtsXj JRPhAc0FrFsLnLCWUQAa8I204yCIbxan6oVeNthlKi0ABuSDkYUpiEtUAfk193OV0xBj 3nw2h9D9pVr4EU+uDcEUkR5JeP3E6XbRDuYOrboFsDDzziQ3QoEhaJLbYZ6/3MPE4C/5 Gvhw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=Oyh1WpmZyRhAh6LbbmL6kVxO7rVD6ZzMLRjNqyG46HQ=; b=m7W0ch8N4iRMPhHUIjl96QAm2iLHXkRJqnPLzRV735ZOF45VGKAoYr3S4+ykpt1zov NHADPkNQUGPUn0zYwOIqAR+FIiI9hbrwfLaW0POHFC3nT2i/wxVRkEA5uVIPQsurHuhm 60YMxb/rP0+h0ulsiIDJbZi3zlRuUhMeAqoax4AkEQuRoI7g6p648SKYuS79F02Ozj6i +HWDAhL3DpaHNFzChPuaoTtuQ9/2A77qjfXCQrlCgcv6RrWc2g8La4msRD7WNnQLkE5K 5XYGBeaBUjYiQ0nCnqCshsQl+9IEe9dtZeQgsCJoMW7cHeDU5WVdlH9eKhxsMgYDCKPn BFSg== X-Gm-Message-State: AOAM531yd9y/dnRjeNe31RtdmFVo2XUKukwmr+u23fKgPxQpy4g042om EsgcEZCm59vSClXkbSaLm+hfrGI= X-Google-Smtp-Source: ABdhPJwkQcf0RK+vCjPRf2wpPS6un2FvXIgGKczdot3qamiaDzc0uiQcQIs7vcL5gcodd2kIESKvN4w= X-Received: from sdf2.svl.corp.google.com ([2620:15c:2c4:201:e6a5:7fa4:f053:e29d]) (user=sdf job=sendgmr) by 2002:a25:dc4:0:b0:641:438e:dd2a with SMTP id 187-20020a250dc4000000b00641438edd2amr10989302ybn.456.1650300648029; Mon, 18 Apr 2022 09:50:48 -0700 (PDT) Date: Mon, 18 Apr 2022 09:50:45 -0700 In-Reply-To: Message-Id: Mime-Version: 1.0 References: <20220414161233.170780-1-sdf@google.com> Subject: Re: [PATCH bpf-next v2] bpf: move rcu lock management out of BPF_PROG_RUN routines From: sdf@google.com To: Alexei Starovoitov Cc: Network Development , bpf , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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