From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx205.postini.com [74.125.245.205]) by kanga.kvack.org (Postfix) with SMTP id 5D97E6B0032 for ; Fri, 23 Aug 2013 13:17:39 -0400 (EDT) Date: Fri, 23 Aug 2013 18:16:05 +0100 From: Catalin Marinas Subject: Re: [BUG] ARM64: Create 4K page size mmu memory map at init time will trigger exception. Message-ID: <20130823171605.GH10971@arm.com> References: <20130822161614.GE1352@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130822161614.GE1352@arm.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Leizhen (ThunderTown, Euler)" Cc: Russell King , "Liujiang (Gerry)" , Will Deacon , "linux-kernel@vger.kernel.org" , Huxinwei , "linux-mm@kvack.org" , Lizefan , "linux-arm-kernel@lists.infradead.org" On Thu, Aug 22, 2013 at 05:16:14PM +0100, Catalin Marinas wrote: > On Thu, Aug 22, 2013 at 04:35:29AM +0100, Leizhen (ThunderTown, Euler) wrote: > > This problem is on ARM64. When CONFIG_ARM64_64K_PAGES is not opened, the memory > > map size can be 2M(section) and 4K(PAGE). First, OS will create map for pgd > > (level 1 table) and level 2 table which in swapper_pg_dir. Then, OS register > > mem block into memblock.memory according to memory node in fdt, like memory@0, > > and create map in setup_arch-->paging_init. If all mem block start address and > > size is integral multiple of 2M, there is no problem, because we will create 2M > > section size map whose entries locate in level 2 table. But if it is not > > integral multiple of 2M, we should create level 3 table, which granule is 4K. > > Now, current implementtion is call early_alloc-->memblock_alloc to alloc memory > > for level 3 table. This function will find a 4K free memory which locate in > > memblock.memory tail(high address), but paging_init is create map from low > > address to high address, so new alloced memory is not mapped, write page talbe > > entry to it will trigger exception. > > I see how this can happen. There is a memblock_set_current_limit to > PGDIR_SIZE (1GB, we have a pre-allocated pmd) and in my tests I had at > least 1GB of RAM which got mapped first and didn't have this problem. > I'll come up with a patch tomorrow. Could you please try this patch? -------------------------8<---------------------------------------