Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757197AbZJLRUQ (ORCPT ); Mon, 12 Oct 2009 13:20:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756257AbZJLRUP (ORCPT ); Mon, 12 Oct 2009 13:20:15 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:47034 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756033AbZJLRUN (ORCPT ); Mon, 12 Oct 2009 13:20:13 -0400 Date: Mon, 12 Oct 2009 19:19:15 +0200 From: Ingo Molnar To: Bjorn Helgaas Cc: Yinghai Lu , Len Brown , Linus Torvalds , Jesse Barnes , Ricardo Jorge da Fonseca Marques Ferreira , Linux Kernel Mailing List , linux-acpi@vger.kernel.org, Yannick Roehlly , Ivan Kokshaysky , x86@kernel.org Subject: Re: [PATCH] pci: increase alignment to make more space for hidden code Message-ID: <20091012171915.GB9596@elte.hu> References: <200908072333.24631.storm@sys49152.net> <4ACAC8F1.1050706@kernel.org> <4AD24B5C.4050905@kernel.org> <200910121059.10366.bjorn.helgaas@hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200910121059.10366.bjorn.helgaas@hp.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1929 Lines: 52 * Bjorn Helgaas wrote: > On Sunday 11 October 2009 03:17:16 pm Yinghai Lu wrote: > > for > > > > http://bugzilla.kernel.org/show_bug.cgi?id=13940 > > > > some system when acpi are enabled, acpi clears some BAR for some devices without > > reason, and kernel will need to allocate devices for them. > > "ACPI clears some BARs"? I'm dubious. The handoff state is the same > whether we boot with "acpi=off" or not, so the BIOS can't be clearing > them. I really don't think the ACPI code in Linux clears BARs. The > Linux PCI code might be clearing BARs, but it sure would be nice to > know exactly why. Did you ever figure that out? > > > try to increase alignment to get more safe range for unassigned devices. > > > > Signed-off-by: Yinghai Lu > > > > --- > > arch/x86/kernel/e820.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > Index: linux-2.6/arch/x86/kernel/e820.c > > =================================================================== > > --- linux-2.6.orig/arch/x86/kernel/e820.c > > +++ linux-2.6/arch/x86/kernel/e820.c > > @@ -1378,8 +1378,8 @@ static unsigned long ram_alignment(resou > > if (mb < 16) > > return 1024*1024; > > > > - /* To 32MB for anything above that */ > > - return 32*1024*1024; > > + /* To 64MB for anything above that */ > > + return 64*1024*1024; > > How do we know 64MB is the correct alignment? > > This feels like a hack that accidentally covers up the problem. I > don't think we understand what's happening well enough. Perhaps hidden chipset BARs getting protected by the larger granularity? Do we know the before/after allocation layout? Ingo -- 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/