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 98429C433EF for ; Tue, 19 Apr 2022 16:32:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354657AbiDSQfY (ORCPT ); Tue, 19 Apr 2022 12:35:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47264 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354653AbiDSQfW (ORCPT ); Tue, 19 Apr 2022 12:35:22 -0400 Received: from mail-pl1-x633.google.com (mail-pl1-x633.google.com [IPv6:2607:f8b0:4864:20::633]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CBF3D28E1C; Tue, 19 Apr 2022 09:32:39 -0700 (PDT) Received: by mail-pl1-x633.google.com with SMTP id s17so5436902plg.9; Tue, 19 Apr 2022 09:32:39 -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=5gBQ8cI8YJwwGK3Rf1VUJH3b+0AkWF9OJOFr2RLSWM8=; b=jYSo2qJIHX3jy8f0McYTLh9SPBxZ/+R3KLCmacexAtZ/hWZBcFC3tOb091zzw38BNO QhDgc0PSuuSUCkF7edBF0YAcp52EawgMxdxzhX4MJIHb4YQHpEroYbu6drLe+7TtPT7h l8fcwra+jD+fufnbQtcJo+V0yVZ4mzlH3H0vRSWoCFysWlHpac5OoNruicW2Q0wdCFD/ 6SWqvrrNVWEeIj5aD83bPnPUXzU3WPQLaeGNE2H36fLLUf6HFs2n3N3/5sbTMw2T/Wui 5qv0xcPnDotOC6CvlnKs7OcS63Wc2MmuUaBuPlL5XdX6J7JO5B34pap3TBh7GEj3AAAn bO7A== 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=5gBQ8cI8YJwwGK3Rf1VUJH3b+0AkWF9OJOFr2RLSWM8=; b=Qs6KudCMFVr/wf7C0DYKFDYrW/B+SN/R4xvqs/WB0jvHpldv0FvgrUOE1EkodLdVJa 1Sx5zMI8CSjO70AQ57wZr8Qx77o2pRf1m1tzQBgQuPHzqyEcGNjCN51G1et+wKn2aADR 15PitjfW8t6prrvymU+t/iJKyvjGKh8ZRND7Asg/0VI55mj8Q5VNbKmedHUXKlF/RB5h AtXZWu/4nHo6pFMd2vys8h+5M8FXBF+6Ku0BEopE5NFrVlZDhmxjnkUrwHfaUyk1+Cze AiWc767K2ooKeDnUeTPxCO9ZesAaJEkshR7nTKWP5MwYegFlhMgISYUPrL+T9nlcf4Pt vTVA== X-Gm-Message-State: AOAM5303mzhoNSHRvxfc1obboYJ2h3/JWtU9+x7HIUS6GphnSgy0IrYY FaFy2ogHXKGnbG+QBl4bxWkW/RmUsRECIsbm1Wxp+fuAlZA= X-Google-Smtp-Source: ABdhPJxkiu+gbut9yp0IFRAEUSWmwSycbpAiTzV37VpWRHSQDJ3nTJ5pQTQ20FYs21G8YFy7DnO+Ig+i5uaZNW7iGks= X-Received: by 2002:a17:903:2d1:b0:156:7ceb:b56f with SMTP id s17-20020a17090302d100b001567cebb56fmr16546506plk.11.1650385959164; Tue, 19 Apr 2022 09:32:39 -0700 (PDT) MIME-Version: 1.0 References: <20220414161233.170780-1-sdf@google.com> In-Reply-To: From: Alexei Starovoitov Date: Tue, 19 Apr 2022 09:32:27 -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 9:20 AM Alexei Starovoitov wrote: > > 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 ? Actually below was enough for gcc 8 and 10: -static int +static __always_inline 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, @@ -55,7 +55,7 @@ bpf_prog_run_array_cg_flags(const struct cgroup_bpf *cgrp, return run_ctx.retval; } -static int +static __always_inline int bpf_prog_run_array_cg(const struct cgroup_bpf *cgrp, we can keep them in .c and generated code looks good. I can apply it with the above change. wdyt?