From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756515AbZBEMrp (ORCPT ); Thu, 5 Feb 2009 07:47:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753777AbZBEMrf (ORCPT ); Thu, 5 Feb 2009 07:47:35 -0500 Received: from smtp-outbound-2.vmware.com ([65.115.85.73]:52537 "EHLO smtp-outbound-2.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753586AbZBEMrf (ORCPT ); Thu, 5 Feb 2009 07:47:35 -0500 Message-ID: <498ADFE3.9020907@vmware.com> Date: Thu, 05 Feb 2009 13:47:31 +0100 From: =?ISO-8859-1?Q?Thomas_Hellstr=F6m?= User-Agent: Thunderbird 2.0.0.17 (X11/20080926) MIME-Version: 1.0 To: Linux kernel mailing list Subject: 2.6.29 pat issue Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! The function in include/linux/mm.h: is_linear_pfn_mapping() doesn't seem valid to me. In particular, we have VMAs to graphics devices in which vma->vm_pgoff is non-zero (Points to an offset in the drm device node), and the VMA is sparsely populated with pfns pointing to uncached discontigous RAM pages. This causes the X86 PAT code to hit the optimized path when it shouldn't, and issue a warning. Also a question about the philosofy behind this strict checking that all PTEs have the same caching attributes: I guess this is only to catch bugs in kernel drivers that don't get this right. At the same time, now that also user-space VMAs are checked this will probably have a significant performance impact. Shouldn't this checking really live behind a debug define? Thanks, Thomas