From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id 396606B0005 for ; Wed, 13 Jul 2016 08:10:12 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id f126so34285808wma.3 for ; Wed, 13 Jul 2016 05:10:12 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id a203si850236wme.4.2016.07.13.05.10.10 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 13 Jul 2016 05:10:10 -0700 (PDT) Subject: Re: [PATCH 0/4] [RFC][v4] Workaround for Xeon Phi PTE A/D bits erratum References: <20160701174658.6ED27E64@viggo.jf.intel.com> <1467412092.7422.56.camel@kernel.crashing.org> <9c09c63c-5c2a-20a4-d68b-a6dc2f88ecaa@suse.cz> From: Vlastimil Babka Message-ID: <829f2f03-8492-841d-869f-7fd7add9cb27@suse.cz> Date: Wed, 13 Jul 2016 14:10:07 +0200 MIME-Version: 1.0 In-Reply-To: <9c09c63c-5c2a-20a4-d68b-a6dc2f88ecaa@suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Benjamin Herrenschmidt , Dave Hansen , linux-kernel@vger.kernel.org Cc: x86@kernel.org, linux-mm@kvack.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, bp@alien8.de, ak@linux.intel.com, mhocko@suse.com On 07/13/2016 01:37 PM, Vlastimil Babka wrote: >> > With the errata, don't you have a situation where a processor in the second >> > category will write and set D despite P having been cleared (due to the >> > race) and thus causing us to miss the transfer of that D to the struct >> > page and essentially completely miss that the physical page is dirty ? > Seems to me like this is indeed possible, but... Nevermind, I have read the v3 thread now, where Dave says [1] that setting the D bit due to the erratum doesn't mean that the page is really actually written to (it's not). So there shouldn't be any true dirty bit to leave behind. [1] http://marc.info/?l=linux-mm&m=146738965614826&w=2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org