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 X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8916BC3A59E for ; Wed, 4 Sep 2019 05:32:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 65D982339D for ; Wed, 4 Sep 2019 05:32:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726010AbfIDFcK (ORCPT ); Wed, 4 Sep 2019 01:32:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32918 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725877AbfIDFcK (ORCPT ); Wed, 4 Sep 2019 01:32:10 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B5D7810277E2; Wed, 4 Sep 2019 05:32:09 +0000 (UTC) Received: from astarta.redhat.com (ovpn-116-92.ams2.redhat.com [10.36.116.92]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5C6A31001DC0; Wed, 4 Sep 2019 05:32:08 +0000 (UTC) From: Yauheni Kaliuta To: Magnus Karlsson Cc: bpf@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH bpf 2/2] libbpf: remove dependency on barrier.h in xsk.h References: <1554792253-27081-1-git-send-email-magnus.karlsson@intel.com> <1554792253-27081-3-git-send-email-magnus.karlsson@intel.com> Date: Wed, 04 Sep 2019 08:32:06 +0300 In-Reply-To: <1554792253-27081-3-git-send-email-magnus.karlsson@intel.com> (Magnus Karlsson's message of "Tue, 9 Apr 2019 08:44:13 +0200") Message-ID: MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.66]); Wed, 04 Sep 2019 05:32:09 +0000 (UTC) Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Hi, Magnus! >>>>> On Tue, 9 Apr 2019 08:44:13 +0200, Magnus Karlsson wrote: > The use of smp_rmb() and smp_wmb() creates a Linux header dependency > on barrier.h that is uneccessary in most parts. This patch implements > the two small defines that are needed from barrier.h. As a bonus, the > new implementations are faster than the default ones as they default > to sfence and lfence for x86, while we only need a compiler barrier in > our case. Just as it is when the same ring access code is compiled in > the kernel. > Fixes: 1cad07884239 ("libbpf: add support for using AF_XDP sockets") > Signed-off-by: Magnus Karlsson > --- > tools/lib/bpf/xsk.h | 19 +++++++++++++++++-- > 1 file changed, 17 insertions(+), 2 deletions(-) > diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h > index 3638147..317b44f 100644 > --- a/tools/lib/bpf/xsk.h > +++ b/tools/lib/bpf/xsk.h > @@ -39,6 +39,21 @@ DEFINE_XSK_RING(xsk_ring_cons); > struct xsk_umem; > struct xsk_socket; > +#if !defined bpf_smp_rmb && !defined bpf_smp_wmb > +# if defined(__i386__) || defined(__x86_64__) > +# define bpf_smp_rmb() asm volatile("" : : : "memory") > +# define bpf_smp_wmb() asm volatile("" : : : "memory") > +# elif defined(__aarch64__) > +# define bpf_smp_rmb() asm volatile("dmb ishld" : : : "memory") > +# define bpf_smp_wmb() asm volatile("dmb ishst" : : : "memory") > +# elif defined(__arm__) > +# define bpf_smp_rmb() asm volatile("dmb ish" : : : "memory") > +# define bpf_smp_wmb() asm volatile("dmb ishst" : : : "memory") > +# else > +# error Architecture not supported by the XDP socket code in libbpf. > +# endif > +#endif > + What about other architectures then? > static inline __u64 *xsk_ring_prod__fill_addr(struct xsk_ring_prod *fill, > __u32 idx) > { > @@ -119,7 +134,7 @@ static inline void xsk_ring_prod__submit(struct xsk_ring_prod *prod, size_t nb) > /* Make sure everything has been written to the ring before signalling > * this to the kernel. > */ > - smp_wmb(); > + bpf_smp_wmb(); > *prod->producer += nb; > } > @@ -133,7 +148,7 @@ static inline size_t xsk_ring_cons__peek(struct xsk_ring_cons *cons, > /* Make sure we do not speculatively read the data before > * we have received the packet buffers from the ring. > */ > - smp_rmb(); > + bpf_smp_rmb(); > *idx = cons->cached_cons; cons-> cached_cons += entries; > -- > 2.7.4 -- WBR, Yauheni Kaliuta