From mboxrd@z Thu Jan 1 00:00:00 1970 From: Muli Ben-Yehuda Subject: Re: [PATCH] Handle vma regions with no backing page Date: Wed, 4 Jun 2008 19:17:55 +0300 Message-ID: <20080604161755.GC7089@il.ibm.com> References: <20080603113937.GE8158@duo.random> <1212592164.26322.10.camel@lnx-benami> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andrea Arcangeli , aliguori@us.ibm.com, Han Weidong , "Kay, Allen M" , Amit Shah , kvm@vger.kernel.org, avi@qumranet.com To: Ben-Ami Yassour1 Return-path: Received: from mtagate2.de.ibm.com ([195.212.29.151]:28283 "EHLO mtagate2.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752371AbYFDSld (ORCPT ); Wed, 4 Jun 2008 14:41:33 -0400 Received: from d12nrmr1607.megacenter.de.ibm.com (d12nrmr1607.megacenter.de.ibm.com [9.149.167.49]) by mtagate2.de.ibm.com (8.13.8/8.13.8) with ESMTP id m54IfQQ6153258 for ; Wed, 4 Jun 2008 18:41:26 GMT Received: from d12av03.megacenter.de.ibm.com (d12av03.megacenter.de.ibm.com [9.149.165.213]) by d12nrmr1607.megacenter.de.ibm.com (8.13.8/8.13.8/NCO v8.7) with ESMTP id m54IfPI44157620 for ; Wed, 4 Jun 2008 20:41:25 +0200 Received: from d12av03.megacenter.de.ibm.com (loopback [127.0.0.1]) by d12av03.megacenter.de.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m54IfP2T008069 for ; Wed, 4 Jun 2008 20:41:25 +0200 Content-Disposition: inline In-Reply-To: <1212592164.26322.10.camel@lnx-benami> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, Jun 04, 2008 at 06:09:24PM +0300, Ben-Ami Yassour1 wrote: > > > We noticed that pfn_valid does not always works as expected by > > > this patch to indicate that a pfn has a backing page. We have > > > seen a case where CONFIG_NUMA was not set and then where > > > pfn_valid returned 1 for an mmio pfn. We then changed the > > > config file with CONFIG_NUMA set and it worked fine as expected > > > (since a different implementation of pfn_valid was used). > > > > > > How should we overcome this issue? > > > > There's a page_is_ram() too, but that's the e820 map check and it > > means it's RAM not that there's a page backing store. Certainly if > > it's not ram we should go ahead with just the pfn but it'd be a > > workaround. > > > > I really think it'd be better off to fix pfn_valid to work for > > NUMA. > > It does work for NUMA, it does not work without the NUMA option. Andrea, how would you suggest to fix pfn_valid for the CONFIG_NUMA disabled case? Cheers, Muli