From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756232AbYBGIga (ORCPT ); Thu, 7 Feb 2008 03:36:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753427AbYBGIgW (ORCPT ); Thu, 7 Feb 2008 03:36:22 -0500 Received: from rv-out-0910.google.com ([209.85.198.186]:35422 "EHLO rv-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753206AbYBGIgV (ORCPT ); Thu, 7 Feb 2008 03:36:21 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=HMd29x4lVrt9Yi0+M5Ge54LnL3VKv6SPPRbpCLsNjbEPXdvF4zzl9ipnOnsF0G5PNJ9pYfyQiuzttT1ChkmNsQAxTSncNT8kO0+W6Xxm33M2HeR4ycCK09k1/kuSCMkhIGdaYRg7FIXfnslAOQikV7ey/AOdEK5zq3UHTYQhfnk= Message-ID: <86802c440802070036w1aced44ft8ab880e8ddeedc85@mail.gmail.com> Date: Thu, 7 Feb 2008 00:36:18 -0800 From: "Yinghai Lu" To: "Ingo Molnar" Subject: Re: [PATCH] x86_64: fix page table size Cc: "Thomas Gleixner" , "H. Peter Anvin" , "Linux Kernel Mailing List" In-Reply-To: <20080207080930.GB28631@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <200802061246.43413.yinghai.lu@sun.com> <200802061501.26533.yinghai.lu@sun.com> <20080206231226.GA6417@elte.hu> <200802062022.44069.yinghai.lu@sun.com> <20080207080930.GB28631@elte.hu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Feb 7, 2008 12:09 AM, Ingo Molnar wrote: > > * Yinghai Lu wrote: > > > [PATCH] x86_64: fix page table size > > > Entering add_active_range(0, 1048576, 67239936) 2 entries of 3200 used > > end_pfn_map = 67239936 > > Kernel panic - not syncing: Overlapping early reservations 8000-109fff > > PGTABLE to 9bc00-9dbff EBDA > > > > change back the logic. we DO need extra space for pmds when > > direct_gbpages is not there. > > > @@ -370,7 +370,7 @@ static void __init find_early_table_space(unsigned long end) > > > > puds = (end + PUD_SIZE - 1) >> PUD_SHIFT; > > tables = round_up(puds * sizeof(pud_t), PAGE_SIZE); > > - if (direct_gbpages) { > > + if (!direct_gbpages) { > > thanks Yinghai, applied! > > I'm wondering why this bug didnt trigger more widely. It seems to me it > needs some serious amount of RAM to trigger this bug - correct? yes. need 256g. 128g without patch it still work. because round_up(.., PAGE_SIZE) get some extra. > > btw., it would be nice to have some "lots of RAM simulation" debugging > code which would just _fake_ a really large e820 map and would in the > end throw away the 'fake' pages later during bootup. Perhaps tell the > early allocator to never allocate into these fake areas [via an struct > e820 entry flag], but all our sizing code and the boot bitmaps, etc. > would be sized accordingly, as if we had this much RAM - and we'd > trigger these nuances. We could put this into a new "fakemem=128GB" boot > option and hence we could boot with fakemem=128GB on a 2GB box and could > at least hope to be able to boot [with some serious amount of RAM wasted > on over-sized pagetables, allocator bitmaps and mem_map[]]. Hm? sound interesting. but need some variable to prevent using non exist page. YH