From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f179.google.com (mail-wi0-f179.google.com [209.85.212.179]) by kanga.kvack.org (Postfix) with ESMTP id 8722D6B0031 for ; Wed, 16 Apr 2014 08:29:00 -0400 (EDT) Received: by mail-wi0-f179.google.com with SMTP id z2so1280195wiv.6 for ; Wed, 16 Apr 2014 05:28:59 -0700 (PDT) Received: from collaborate-mta1.arm.com (fw-tnat.austin.arm.com. [217.140.110.23]) by mx.google.com with ESMTP id r7si6624273wjw.198.2014.04.16.05.28.58 for ; Wed, 16 Apr 2014 05:28:59 -0700 (PDT) Message-ID: <534E777C.1090605@arm.com> Date: Wed, 16 Apr 2014 13:28:44 +0100 From: Marc Zyngier MIME-Version: 1.0 Subject: Re: [PATCH v2] ARM: mm: support big-endian page tables References: <5301B4AF.1040305@huawei.com> <5327F75F.1010406@huawei.com> <20140414104300.GA3530@arm.com> <534BC31A.7060705@arm.com> <534DEEDD.5030203@huawei.com> In-Reply-To: <534DEEDD.5030203@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Jianguo Wu Cc: Will Deacon , "linux@arm.linux.org.uk" , Wang Nan , "gregkh@linuxfoundation.org" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Li Zefan , Catalin Marinas , Ben Dooks , "linux-arm-kernel@lists.infradead.org" On 16/04/14 03:45, Jianguo Wu wrote: > On 2014/4/14 19:14, Marc Zyngier wrote: > >> On 14/04/14 11:43, Will Deacon wrote: >>> (catching up on old email) >>> >>> On Tue, Mar 18, 2014 at 07:35:59AM +0000, Jianguo Wu wrote: >>>> Cloud you please take a look at this? >>> >>> [...] >>> >>>> On 2014/2/17 15:05, Jianguo Wu wrote: >>>>> When enable LPAE and big-endian in a hisilicon board, while specify >>>>> mem=384M mem=512M@7680M, will get bad page state: >>>>> >>>>> Freeing unused kernel memory: 180K (c0466000 - c0493000) >>>>> BUG: Bad page state in process init pfn:fa442 >>>>> page:c7749840 count:0 mapcount:-1 mapping: (null) index:0x0 >>>>> page flags: 0x40000400(reserved) >>>>> Modules linked in: >>>>> CPU: 0 PID: 1 Comm: init Not tainted 3.10.27+ #66 >>>>> [] (unwind_backtrace+0x0/0x11c) from [] (show_stack+0x10/0x14) >>>>> [] (show_stack+0x10/0x14) from [] (bad_page+0xd4/0x104) >>>>> [] (bad_page+0xd4/0x104) from [] (free_pages_prepare+0xa8/0x14c) >>>>> [] (free_pages_prepare+0xa8/0x14c) from [] (free_hot_cold_page+0x18/0xf0) >>>>> [] (free_hot_cold_page+0x18/0xf0) from [] (handle_pte_fault+0xcf4/0xdc8) >>>>> [] (handle_pte_fault+0xcf4/0xdc8) from [] (handle_mm_fault+0xf4/0x120) >>>>> [] (handle_mm_fault+0xf4/0x120) from [] (do_page_fault+0xfc/0x354) >>>>> [] (do_page_fault+0xfc/0x354) from [] (do_DataAbort+0x2c/0x90) >>>>> [] (do_DataAbort+0x2c/0x90) from [] (__dabt_usr+0x34/0x40) >>> >>> [...] >>> >>>>> The bug is happened in cpu_v7_set_pte_ext(ptep, pte): >>>>> when pte is 64-bit, for little-endian, will store low 32-bit in r2, >>>>> high 32-bit in r3; for big-endian, will store low 32-bit in r3, >>>>> high 32-bit in r2, this will cause wrong pfn stored in pte, >>>>> so we should exchange r2 and r3 for big-endian. >>> > > Hi Marc, > How about this: > > The bug is happened in cpu_v7_set_pte_ext(ptep, pte): > - It tests the L_PTE_NONE in one word on the other, and possibly clear L_PTE_VALID > tst r3, #1 << (57 - 32) @ L_PTE_NONE > bicne r2, #L_PTE_VALID > - Same for L_PTE_DIRTY, respectively setting L_PTE_RDONLY > > As for LPAE, the pte is 64-bits, and the value of r2/r3 is depending on the endianness, > for little-endian, will store low 32-bit in r2, high 32-bit in r3, > for big-endian, will store low 32-bit in r3, high 32-bit in r2, > this will cause wrong bit is cleared or set, and get wrong pfn. > So we should exchange r2 and r3 for big-endian. May I suggest the following instead: "An LPAE PTE is a 64bit quantity, passed to cpu_v7_set_pte_ext in the r2 and r3 registers. On an LE kernel, r2 contains the LSB of the PTE, and r3 the MSB. On a BE kernel, the assignment is reversed. Unfortunately, the current code always assumes the LE case, leading to corruption of the PTE when clearing/setting bits. This patch fixes this issue much like it has been done already in the cpu_v7_switch_mm case." Cheers, M. -- Jazz is not dead. It just smells funny... -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org