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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT 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 71CE1C433F5 for ; Thu, 6 Sep 2018 19:29:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 11D9420869 for ; Thu, 6 Sep 2018 19:29:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="gDpMJdzc" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 11D9420869 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729739AbeIGAGG (ORCPT ); Thu, 6 Sep 2018 20:06:06 -0400 Received: from merlin.infradead.org ([205.233.59.134]:48606 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726265AbeIGAGF (ORCPT ); Thu, 6 Sep 2018 20:06:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=zt5lShDTuY1ZzO+3P83YEWISa3s6DGfkvvVHNsgF6p4=; b=gDpMJdzcePMVY7vNLpRIuFaGe zIXLOHxY4zr3I2RU8ZGNt/vS+WxCKbIkTrDTlxm7EGOm4A/nUMCb5kWDDbhaSHK+chQ7ODnyt0C5g 6SYOQQZjZPUR3o+qQ3QEI0/aN3OjLOHdPf9Jt2jF7syXLxtXCoJPh82u9c1Fs/4RJX2c2lsdoThdi 5Pj9p8vxx0zkQhznBLHEfWO3vEDBJxgZz8btTFHr1WehpPVEAmktlDgbHbIU1jjHywXgv5kPE9P+i Yb0Dr4NS1zAhw7eK+hH/1mlAyfR23FXhatQVNGjCSlzaX2vMRucdqZWp1Hqxg8mKE1vB0CzNFVfR0 rUPdzmHNg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fxzxc-0004b8-A6; Thu, 06 Sep 2018 19:29:01 +0000 Received: by worktop (Postfix, from userid 1000) id BA7D66E0AA9; Thu, 6 Sep 2018 21:28:52 +0200 (CEST) Date: Thu, 6 Sep 2018 21:28:52 +0200 From: Peter Zijlstra To: Dave Hansen Cc: Nadav Amit , Thomas Gleixner , linux-kernel@vger.kernel.org, Ingo Molnar , x86@kernel.org, Dave Hansen , Nadav Amit , Andi Kleen , Josh Poimboeuf , Michal Hocko , Vlastimil Babka , Sean Christopherson , Andy Lutomirski Subject: Re: [PATCH] x86: use WRITE_ONCE() when setting PTEs Message-ID: <20180906192852.GC4816@worktop.programming.kicks-ass.net> References: <20180902181451.80520-1-namit@vmware.com> <8aef58c7-c27c-5df8-69b3-b188dd5f64e8@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8aef58c7-c27c-5df8-69b3-b188dd5f64e8@intel.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 06, 2018 at 10:21:38AM -0700, Dave Hansen wrote: > There's probably a massive number of things that would break if we > assumed sane 64-bit writes can be observed piecemeal. Do assume, it has been observed. WRITE_ONCE()/READ_ONCE() are _required_ if you cannot have load/store tearing.