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=-5.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 3F910C433DF for ; Mon, 20 Jul 2020 15:29:10 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0CE5A22482 for ; Mon, 20 Jul 2020 15:29:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=citrix.com header.i=@citrix.com header.b="EuDAFR34" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0CE5A22482 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=citrix.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jxXil-0003T8-Od; Mon, 20 Jul 2020 15:28:51 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jxXij-0003T3-UC for xen-devel@lists.xenproject.org; Mon, 20 Jul 2020 15:28:49 +0000 X-Inumbo-ID: b502edba-ca9d-11ea-9fc5-12813bfff9fa Received: from esa5.hc3370-68.iphmx.com (unknown [216.71.155.168]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id b502edba-ca9d-11ea-9fc5-12813bfff9fa; Mon, 20 Jul 2020 15:28:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=citrix.com; s=securemail; t=1595258928; h=subject:to:cc:references:from:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=dHkoChAb7fbL9I2v1zRaA2LTj9xG8/LBS67LHiUSLVU=; b=EuDAFR34NnElUE6ynL4NU4mlzfN3IV+ek6ZcgRjdA1aNngosI2d5EIDF qUwgD36JjSgyV6K2H2R+g8ynCdGGLXLsJ8FoWRWQx5vkwjAljwjeERRqX YDTCzvskwSmKJZtgrqvmml/bOJV3zx2yVwYbdbGBG63JSGYFx0OilSiSt s=; Authentication-Results: esa5.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none IronPort-SDR: E/KP/Tzve8NqTkwIRxA2gIUDMfLET6xYCGtDmozU41iJ0P858ydhiU13QJiNDAel4nTItjGPAv KSz1dy+D2e3eX1peVF+JbYKBj1iAluMtVqWEi3wK0xXO2mna0xq70n4oIfJkMiCPmr46Hret+T udbdAZmDP2lq4LMEQgw8rD/WKPac5TcUH1prg0XF4wgqB1x5bpCkPWFpxK+kFNC7ObtMgeihiS A+jAqIZO3jOeF3uTRYMFCKB0EKJBgEg+UrqbtZi3b0Ud5y4wvNSsdYZshGSSChv7D23znxLVe0 ZGI= X-SBRS: 2.7 X-MesageID: 22960947 X-Ironport-Server: esa5.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.75,375,1589256000"; d="scan'208";a="22960947" Subject: Re: [PATCH v3 1/2] x86: restore pv_rtc_handler() invocation To: Jan Beulich , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= References: <5426dd6f-50cd-dc23-5c6b-0ab631d98d38@suse.com> <7dd4b668-06ca-807a-9cc1-77430b2376a8@suse.com> <20200715121347.GY7191@Air-de-Roger> <2b9de0fd-5973-ed66-868c-ffadca83edf3@suse.com> <20200715133217.GZ7191@Air-de-Roger> <20200715145144.GA7191@Air-de-Roger> From: Andrew Cooper Message-ID: <01509d7d-4cf3-7f3f-4aa1-eaa3b1d3b95b@citrix.com> Date: Mon, 20 Jul 2020 16:28:24 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Language: en-GB X-ClientProxiedBy: AMSPEX02CAS01.citrite.net (10.69.22.112) To AMSPEX02CL02.citrite.net (10.69.22.126) X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: "xen-devel@lists.xenproject.org" , Wei Liu , Paul Durrant Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 16/07/2020 11:06, Jan Beulich wrote: > ACCESS_ONCE() guarantees single access, but doesn't guarantee that > the compiler wouldn't split this single access into multiple insns. ACCESS_ONCE() does guarantee single accesses for any natural integer size. There is a section about this specifically in Linux's memory-barriers.txt, and this isn't the first time I've pointed it out... ~Andrew