From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932259Ab2K1TKG (ORCPT ); Wed, 28 Nov 2012 14:10:06 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:26223 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932209Ab2K1TKD (ORCPT ); Wed, 28 Nov 2012 14:10:03 -0500 Date: Wed, 28 Nov 2012 14:09:02 -0500 From: Konrad Rzeszutek Wilk To: Yinghai Lu Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Jacob Shin , Andrew Morton , Stefano Stabellini , linux-kernel@vger.kernel.org Subject: Re: [PATCH v8 34/46] x86, mm: Add check before clear pte above max_low_pfn on 32bit Message-ID: <20121128190902.GS21266@phenom.dumpdata.com> References: <1353123563-3103-1-git-send-email-yinghai@kernel.org> <1353123563-3103-35-git-send-email-yinghai@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1353123563-3103-35-git-send-email-yinghai@kernel.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: ucsinet21.oracle.com [156.151.31.93] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 16, 2012 at 07:39:11PM -0800, Yinghai Lu wrote: > During test patch that adjust page_size_mask to map small range ram with > big page size, found page table is setup wrongly for 32bit. And Which patch is that? x86, mm: Add global page_size_mask and probe one time only Can you include the name here please. > native_pagetable_init wrong clear pte for pmd with large page support. ^^^^^-> wrongly cleared > > 1. add more comments about why we are expecting pte. > > 2. add BUG checking, so next time we could find problem earlier > when we mess up page table setup again. Not very optimistic about future changes, eh? > > 3. max_low_pfn is not included boundary for low memory mapping. > We should check from max_low_pfn instead of +1. > > 4. add print out when some pte really get cleared, or we should use > WARN() to find out why above max_low_pfn get mapped? so we could > fix it. I would think WARN? Easier to spot and get bug emails. > > Signed-off-by: Yinghai Lu > --- > arch/x86/mm/init_32.c | 18 ++++++++++++++++-- > 1 files changed, 16 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c > index 322ee56..19ef9f0 100644 > --- a/arch/x86/mm/init_32.c > +++ b/arch/x86/mm/init_32.c > @@ -480,9 +480,14 @@ void __init native_pagetable_init(void) > > /* > * Remove any mappings which extend past the end of physical > - * memory from the boot time page table: > + * memory from the boot time page table. > + * In virtual address space, we should have at least two pages > + * from VMALLOC_END to pkmap or fixmap according to VMALLOC_END > + * definition. And max_low_pfn is set to VMALLOC_END physical > + * address. If initial memory mapping is doing right job, we > + * should have pte used near max_low_pfn or one pmd is not present. 'have pte used near' ? Do you mean we should have an used PTE near max_low_pfn and one empty PMD? > */ > - for (pfn = max_low_pfn + 1; pfn < 1<<(32-PAGE_SHIFT); pfn++) { > + for (pfn = max_low_pfn; pfn < 1<<(32-PAGE_SHIFT); pfn++) { > va = PAGE_OFFSET + (pfn< pgd = base + pgd_index(va); > if (!pgd_present(*pgd)) > @@ -493,10 +498,19 @@ void __init native_pagetable_init(void) > if (!pmd_present(*pmd)) > break; > > + /* should not be large page here */ > + if (pmd_large(*pmd)) { > + pr_warn("try to clear pte for ram above max_low_pfn: pfn: %lx pmd: %p pmd phys: %lx, but pmd is big page and is not using pte !\n", > + pfn, pmd, __pa(pmd)); > + BUG_ON(1); > + } > + > pte = pte_offset_kernel(pmd, va); > if (!pte_present(*pte)) > break; > > + printk(KERN_DEBUG "clearing pte for ram above max_low_pfn: pfn: %lx pmd: %p pmd phys: %lx pte: %p pte phys: %lx\n", > + pfn, pmd, __pa(pmd), pte, __pa(pte)); > pte_clear(NULL, va, pte); > } > paravirt_alloc_pmd(&init_mm, __pa(base) >> PAGE_SHIFT); > -- > 1.7.7