From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752030AbYL3Hyo (ORCPT ); Tue, 30 Dec 2008 02:54:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750954AbYL3Hye (ORCPT ); Tue, 30 Dec 2008 02:54:34 -0500 Received: from cantor2.suse.de ([195.135.220.15]:47832 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750858AbYL3Hyd (ORCPT ); Tue, 30 Dec 2008 02:54:33 -0500 Date: Tue, 30 Dec 2008 08:54:28 +0100 From: Nick Piggin To: Ingo Molnar Cc: Andrew Morton , ebiederm@xmission.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, ijc@hellion.org.uk Subject: Re: early fixmap causes kmap breakage Message-ID: <20081230075428.GC14132@wotan.suse.de> References: <20081218211543.GB10681@wotan.suse.de> <20081229151731.2a2c5a02.akpm@linux-foundation.org> <20081230040118.GA27679@wotan.suse.de> <20081230061344.GA28281@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081230061344.GA28281@elte.hu> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 30, 2008 at 07:13:44AM +0100, Ingo Molnar wrote: > > * Nick Piggin wrote: > > > On Mon, Dec 29, 2008 at 03:17:31PM -0800, Andrew Morton wrote: > > > On Thu, 18 Dec 2008 22:15:43 +0100 > > > Nick Piggin wrote: > > > > > > > Hi, > > > > > > > > I've debugged a problem where i386+pae systems with more than a few CPUs > > > > blow up at boot in the kmap_atomic code. > > > > > > ping? > > > > No further progress here, I'm waiting on input for how to fix this > > "nicely". Meantime, clearing the early fixmap pte I guess works, but you > > lose a page... is it possible to put it into .initdata or is there some > > issue with that? (I guess on a PAE kernel, 4K isn't a big deal). > > yeah, 4K shouldnt be a big deal. Mind sending a patch for this? I don't know if we should put a warning when we encounter this condition, to help catch other unintended uses... But this at least clears out the early fixmap pte and provides a contiguous allocation... --- arch/x86/mm/init_32.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) Index: linux-2.6/arch/x86/mm/init_32.c =================================================================== --- linux-2.6.orig/arch/x86/mm/init_32.c +++ linux-2.6/arch/x86/mm/init_32.c @@ -155,6 +155,7 @@ page_table_range_init(unsigned long star unsigned long vaddr; pgd_t *pgd; pmd_t *pmd; + pte_t *lastpte = NULL; vaddr = start; pgd_idx = pgd_index(vaddr); @@ -166,7 +167,19 @@ page_table_range_init(unsigned long star pmd = pmd + pmd_index(vaddr); for (; (pmd_idx < PTRS_PER_PMD) && (vaddr != end); pmd++, pmd_idx++) { - one_page_table_init(pmd); + pte_t *pte; + + pte = one_page_table_init(pmd); + if (lastpte && lastpte + PTRS_PER_PTE != pte) { + pte_t *newpte; + + pmd_clear(pmd); + newpte = one_page_table_init(pmd); + BUG_ON(lastpte + PTRS_PER_PTE != newpte); + memset(newpte, pte, PAGE_SIZE); + pte = lastpte; + } + lastpte = pte; vaddr += PMD_SIZE; }