Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757292AbYAJW2V (ORCPT ); Thu, 10 Jan 2008 17:28:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754855AbYAJW2O (ORCPT ); Thu, 10 Jan 2008 17:28:14 -0500 Received: from mga02.intel.com ([134.134.136.20]:38760 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754596AbYAJW2N convert rfc822-to-8bit (ORCPT ); Thu, 10 Jan 2008 17:28:13 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.24,268,1196668800"; d="scan'208";a="320860814" X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Subject: RE: [patch 02/11] PAT x86: Map only usable memory in x86_64 identity map and kernel text Date: Thu, 10 Jan 2008 14:27:10 -0800 Message-ID: <924EFEDD5F540B4284297C4DC59F3DEE5A29A5@orsmsx423.amr.corp.intel.com> In-Reply-To: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [patch 02/11] PAT x86: Map only usable memory in x86_64 identity map and kernel text Thread-Index: AchT1vutDkseaWHxSx+H9vyaOSC7agAAMqiw References: <20080110184840.927409000@intel.com> <20080110184854.787474000@intel.com> <924EFEDD5F540B4284297C4DC59F3DEE5A2958@orsmsx423.amr.corp.intel.com> From: "Pallipadi, Venkatesh" To: "Linus Torvalds" Cc: , , , , , , , , , , "Barnes, Jesse" , , , "Siddha, Suresh B" X-OriginalArrivalTime: 10 Jan 2008 22:26:19.0793 (UTC) FILETIME=[D2B0B810:01C853D7] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1936 Lines: 53 >-----Original Message----- >From: Linus Torvalds [mailto:torvalds@linux-foundation.org] >Sent: Thursday, January 10, 2008 2:15 PM >To: Pallipadi, Venkatesh >Cc: ak@muc.de; ebiederm@xmission.com; rdreier@cisco.com; >gregkh@suse.de; airlied@skynet.ie; davej@redhat.com; >mingo@elte.hu; tglx@linutronix.de; akpm@linux-foundation.org; >arjan@infradead.org; Barnes, Jesse; davem@davemloft.net; >linux-kernel@vger.kernel.org; Siddha, Suresh B >Subject: RE: [patch 02/11] PAT x86: Map only usable memory in >x86_64 identity map and kernel text > > > >On Thu, 10 Jan 2008, Pallipadi, Venkatesh wrote: >> >> Yes. I had those pages not mapped at all earlier. The reason >I switched >> to zero page is to continue support cases like: >> BIOS-e820: 0000000000000000 - 000000000009cc00 (usable) >> BIOS-e820: 000000000009cc00 - 00000000000a0000 (reserved) >> BIOS-e820: 00000000000cc000 - 00000000000d0000 (reserved) >> BIOS-e820: 00000000000e4000 - 0000000000100000 (reserved) >> BIOS-e820: 0000000000100000 - 00000000cff60000 (usable) >> >> In this case if some one does a dd of /dev/mem before they >can read the >> contents of usable memory in 0x100000-0xcff60000 range. > >Well, I think that /dev/mem should simply give them the right >info. That's >what people use /dev/mem for - doing things like reading BIOS >images etc. > >So returning *either* a zero page *or* stopping at the first >hole is both >equally wrong. > I was not fully clear in my earlier email. Mapping /dev/mem would still work with our changes. As they go through proper map interface. It is the dd of dev mem which does the read that has the problem. I was wondering of apps using dd. Thanks, Venki -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/