From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934768AbYBTUpm (ORCPT ); Wed, 20 Feb 2008 15:45:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755034AbYBTUpB (ORCPT ); Wed, 20 Feb 2008 15:45:01 -0500 Received: from mx1.redhat.com ([66.187.233.31]:56921 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752362AbYBTUpA (ORCPT ); Wed, 20 Feb 2008 15:45:00 -0500 Date: Wed, 20 Feb 2008 15:44:22 -0500 From: Vivek Goyal To: mingo@elte.hu Cc: stable@kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Andi Kleen Subject: Re: [patch 1/3] x86_64: CPA, fix cache attribute inconsistency bug, v2.6.22 backport Message-ID: <20080220204422.GE7415@redhat.com> References: <20080215195508.GA12405@elte.hu> <20080215195821.GA15432@elte.hu> <20080220203018.GD7415@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080220203018.GD7415@redhat.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 20, 2008 at 03:30:18PM -0500, Vivek Goyal wrote: > On Fri, Feb 15, 2008 at 08:58:22PM +0100, Ingo Molnar wrote: > > > > fix CPA cache attribute bug in v2.6.23. When phys_base is nonzero > > (when CONFIG_RELOCATABLE=y) then change_page_attr_addr() miscalculates > > the secondary alias address by -14 MB (depending on the configured > > offset). > > > > The default 64-bit kernels of Fedora and Ubuntu are affected: > > > > $ grep RELOCA /boot/config-2.6.23.9-85.fc8 > > CONFIG_RELOCATABLE=y > > > > $ grep RELOC /boot/config-2.6.22-14-generic > > CONFIG_RELOCATABLE=y > > > > and probably on many other distros as well. > > > > the bug affects all pages in the first 40 MB of physical RAM that > > are allocated by some subsystem that does ioremap_nocache() on them: > > > > if (__pa(address) < KERNEL_TEXT_SIZE) { > > > > Hence we might leave page table entries with inconsistent cache > > attributes around (pages mapped at both UnCacheable and Write-Back), > > and we can also set the wrong kernel text pages to UnCacheable. > > > > the effects of this bug can be random slowdowns and other misbehavior. > > If for example AGP allocates its aperture pages into the first 40 MB > > of physical RAM, then the -14 MB bug might mark random kernel texto > > pages as uncacheable, slowing down a random portion of the 64-bit > > kernel until the AGP driver is unloaded. > > > > Signed-off-by: Ingo Molnar > > Acked-by: Thomas Gleixner > > --- > > arch/x86_64/mm/pageattr.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > Index: linux-tmp/arch/x86_64/mm/pageattr.c > > =================================================================== > > --- linux-tmp.orig/arch/x86_64/mm/pageattr.c > > +++ linux-tmp/arch/x86_64/mm/pageattr.c > > @@ -204,7 +204,7 @@ int change_page_attr_addr(unsigned long > > if (__pa(address) < KERNEL_TEXT_SIZE) { > > Hi Ingo, > > Should we change above condition also to something like following. > > kernel_phys_start = __pa(__START_KERNEL_map) + phys_base Oops. Just noticed that __pa() is already taking care of adding phys_base. So it should probably be. kernel_phys_start = __pa(__START_KERNEL_map); kernel_phys_end = kernel_phys_start + KERNEL_TEXT_SIZE; if (__pa(address) >= kernel_phys_start && __pa(address) <= kernel_phys_end) Thanks Vivek