From patchwork Mon Dec 12 03:08:08 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Xu X-Patchwork-Id: 9469985 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 6321160476 for ; Mon, 12 Dec 2016 03:09:04 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5635C28307 for ; Mon, 12 Dec 2016 03:09:04 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4AE3E2840E; Mon, 12 Dec 2016 03:09:04 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id F378328307 for ; Mon, 12 Dec 2016 03:09:03 +0000 (UTC) Received: from localhost ([::1]:58312 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cGGz9-0002f8-3S for patchwork-qemu-devel@patchwork.kernel.org; Sun, 11 Dec 2016 22:09:03 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55143) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cGGyg-0002e4-6y for qemu-devel@nongnu.org; Sun, 11 Dec 2016 22:08:34 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cGGyf-0003Lo-EC for qemu-devel@nongnu.org; Sun, 11 Dec 2016 22:08:34 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56161) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cGGyf-0003LM-9n for qemu-devel@nongnu.org; Sun, 11 Dec 2016 22:08:33 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 83E6AC057FA9; Mon, 12 Dec 2016 03:08:32 +0000 (UTC) Received: from pxdev.xzpeter.org (vpn1-5-149.pek2.redhat.com [10.72.5.149]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id uBC38M7t005906; Sun, 11 Dec 2016 22:08:29 -0500 From: Peter Xu To: qemu-devel@nongnu.org, kvm@vger.kernel.org Date: Mon, 12 Dec 2016 11:08:08 +0800 Message-Id: <1481512100-10380-3-git-send-email-peterx@redhat.com> In-Reply-To: <1481512100-10380-1-git-send-email-peterx@redhat.com> References: <1481512100-10380-1-git-send-email-peterx@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Mon, 12 Dec 2016 03:08:32 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [kvm-unit-tests PATCH v8 02/14] x86/asm: add cpu_relax() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: drjones@redhat.com, rkrcmar@redhat.com, peterx@redhat.com, agordeev@redhat.com, jan.kiszka@web.de, pbonzini@redhat.com Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP This will be useful to be put inside loops. Suggested-by: Andrew Jones Reviewed-by: Andrew Jones Signed-off-by: Peter Xu --- lib/x86/asm/barrier.h | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/lib/x86/asm/barrier.h b/lib/x86/asm/barrier.h index 7c108bd..193fb4c 100644 --- a/lib/x86/asm/barrier.h +++ b/lib/x86/asm/barrier.h @@ -13,4 +13,15 @@ #define smp_rmb() barrier() #define smp_wmb() barrier() +/* REP NOP (PAUSE) is a good thing to insert into busy-wait loops. */ +static inline void rep_nop(void) +{ + asm volatile("rep; nop" ::: "memory"); +} + +static inline void cpu_relax(void) +{ + rep_nop(); +} + #endif