From patchwork Tue Apr 11 09:49:21 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Wanpeng Li X-Patchwork-Id: 9674813 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 9845C60382 for ; Tue, 11 Apr 2017 09:49:42 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 756892851D for ; Tue, 11 Apr 2017 09:49:42 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 69F6E2852B; Tue, 11 Apr 2017 09:49:42 +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=-6.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, RCVD_IN_SORBS_SPAM autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2B31C2851D for ; Tue, 11 Apr 2017 09:49:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753210AbdDKJta (ORCPT ); Tue, 11 Apr 2017 05:49:30 -0400 Received: from mail-pg0-f65.google.com ([74.125.83.65]:35433 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753162AbdDKJt3 (ORCPT ); Tue, 11 Apr 2017 05:49:29 -0400 Received: by mail-pg0-f65.google.com with SMTP id g2so29080058pge.2; Tue, 11 Apr 2017 02:49:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=nxdAWf3cNXZseCltINsOFlvJTSBKvZKKIYtHoRaLtaI=; b=cwYzFsPVMjcKPuB5oNcOYuXde+zW/eO94s1O1UHa9SFFsLI8057PrdyLSfANJIZ1Ps 4tDPBpwK3YjW65Ik5uzAbw24AymzbR0spWaQQj6FNwPcAap6sq996r5/lLIkQPUDLJT5 M7Hkj81Gkg/UdHb2OXGkAIaur71LuaAxDzs3U8oYTMS0y3dtMGWX7cMVX1RD8WNNZbPt BvZYuqtdr/Vg/hIAlxPGmlmrlkSNJYFBxkC1sWCMIgoenM5t38THlzFbEPP2OHzlX7Fb zKLhBl5MF8SWPbQ1Oy+H+G+XzI+9EuVUY24JXcDq8VoaXKV6Kb8nZRcZazHvMwK04FQO UUPg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=nxdAWf3cNXZseCltINsOFlvJTSBKvZKKIYtHoRaLtaI=; b=l+lmVvPppsBmWaibXUDWMwVnMmcPpacw7l32LqKqLhG87H1uhtWTjusv1MUAddWc7I OJw1HDyJPET0EglDa0NCN0fqtJTWUMtpzAksTc+BQvsQaq1SvcR5b8A81c6wPLd8aFoK GpWWZ0jZN2kWDD0fQlCWYJ2PzQsG4J4Xo4GeDXn5iiR8njcjPUQavpxDWQJ7nb+3FdaU myraxHSTt/BSY3yRIQgDj9Guaj2JCpT8VicTYFjjQj8/DAyDyAF3oaFP2VbP2K8/QgjU 1p530m3AuFj5zUKLCLLw9EeUKaqyepoag2mo12C/brl5TX9dmwEJPnJyTDVVaahHMDVB Z7Kg== X-Gm-Message-State: AFeK/H3sGVTD15Lr95pzk8nIjnn4wanLltZYrKZi+Klb4uDTznJMnR0Z4LnrwQNmXCb/eg== X-Received: by 10.98.20.203 with SMTP id 194mr58710306pfu.70.1491904168331; Tue, 11 Apr 2017 02:49:28 -0700 (PDT) Received: from localhost ([203.205.141.123]) by smtp.gmail.com with ESMTPSA id f5sm29600742pgn.50.2017.04.11.02.49.27 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 11 Apr 2017 02:49:27 -0700 (PDT) From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Wanpeng Li Subject: [PATCH] x86/kvm: virt_xxx memory barriers instead of mandatory barriers Date: Tue, 11 Apr 2017 02:49:21 -0700 Message-Id: <1491904161-4099-1-git-send-email-wanpeng.li@hotmail.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Wanpeng Li virt_xxx memory barriers are implemented trivially using the low-level __smp_xxx macros, __smp_xxx is equal to a compiler barrier for strong TSO memory model, however, mandatory barriers will unconditional add memory barriers, this patch replaces the rmb() in kvm_steal_clock() by virt_rmb(). Cc: Paolo Bonzini Cc: Radim Krčmář Signed-off-by: Wanpeng Li Reviewed-by: Paolo Bonzini --- arch/x86/kernel/kvm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 14f65a5..da5c097 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -396,9 +396,9 @@ static u64 kvm_steal_clock(int cpu) src = &per_cpu(steal_time, cpu); do { version = src->version; - rmb(); + virt_rmb(); steal = src->steal; - rmb(); + virt_rmb(); } while ((version & 1) || (version != src->version)); return steal;