Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753632AbYJ3CqT (ORCPT ); Wed, 29 Oct 2008 22:46:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752257AbYJ3CqJ (ORCPT ); Wed, 29 Oct 2008 22:46:09 -0400 Received: from byss.tchmachines.com ([208.76.80.75]:59874 "EHLO byss.tchmachines.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752053AbYJ3CqI (ORCPT ); Wed, 29 Oct 2008 22:46:08 -0400 X-Greylist: delayed 2637 seconds by postgrey-1.27 at vger.kernel.org; Wed, 29 Oct 2008 22:46:08 EDT Date: Wed, 29 Oct 2008 19:02:03 -0700 From: Ravikiran G Thirumalai To: Ingo Molnar Cc: venkatesh.pallipadi@intel.com, linux-kernel@vger.kernel.org, tim@scalemp.com, shai@scalex86.org Subject: [patch] x86: Fix /dev/mem mmap breakage when PAT is disabled Message-ID: <20081030020203.GA12423@localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.15+20070412 (2007-04-11) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - byss.tchmachines.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - scalex86.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1595 Lines: 43 Fix mmap to /dev/mem when CONFIG_X86_PAT is off and CONFIG_STRICT_DEVMEM is off mmap to /dev/mem on kernel memory has been failing since the introduction of PAT (CONFIG_STRICT_DEVMEM=n case). Seems like the check to avoid cache aliasing with PAT is kicking in even when PAT is disabled. The bug seems to have crept in 2.6.26. This patch makes sure that mmap to regular kernel memory succeeds if CONFIG_STRICT_DEVMEM=n and PAT is disabled. The checks to avoid cache aliasing still happens if PAT is enabled. Signed-off-by: Ravikiran Thirumalai Tested-by: Tim Sirianni Index: git.tip/arch/x86/mm/pat.c =================================================================== --- git.tip.orig/arch/x86/mm/pat.c 2008-10-21 14:02:57.000000000 -0700 +++ git.tip/arch/x86/mm/pat.c 2008-10-29 13:19:47.000000000 -0800 @@ -481,6 +481,7 @@ return 1; } #else +/* This check is needed to avoid cache aliasing when PAT is enabled */ static inline int range_is_allowed(unsigned long pfn, unsigned long size) { u64 from = ((u64)pfn) << PAGE_SHIFT; @@ -508,7 +509,8 @@ unsigned long flags = -1; int retval; - if (!range_is_allowed(pfn, size)) + /* Ensure cache aliasing does not occur if and only if PAT is on */ + if (pat_enabled && !range_is_allowed(pfn, size)) return 0; if (file->f_flags & O_SYNC) { -- 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/