From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f180.google.com (mail-wi0-f180.google.com [209.85.212.180]) by kanga.kvack.org (Postfix) with ESMTP id 819176B00DC for ; Mon, 14 Apr 2014 07:14:40 -0400 (EDT) Received: by mail-wi0-f180.google.com with SMTP id q5so3819970wiv.1 for ; Mon, 14 Apr 2014 04:14:38 -0700 (PDT) Received: from collaborate-mta1.arm.com (fw-tnat.austin.arm.com. [217.140.110.23]) by mx.google.com with ESMTP id i17si5068017wjq.235.2014.04.14.04.14.37 for ; Mon, 14 Apr 2014 04:14:38 -0700 (PDT) Message-ID: <534BC31A.7060705@arm.com> Date: Mon, 14 Apr 2014 12:14:34 +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> In-Reply-To: <20140414104300.GA3530@arm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Will Deacon Cc: Jianguo Wu , "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 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. > > I believe that Marc (added to CC) has been running LPAE-enabled, big-endian > KVM guests without any issues, so it seems unlikely that we're storing the > PTEs backwards. Can you check the configuration of SCTLR.EE? So, for the record: root@when-the-lie-s-so-big:~# cat /proc/cpuinfo processor : 0 model name : ARMv7 Processor rev 4 (v7b) Features : swp half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm CPU implementer : 0x41 CPU architecture: 7 CPU variant : 0x0 CPU part : 0xc07 CPU revision : 4 processor : 1 model name : ARMv7 Processor rev 4 (v7b) Features : swp half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm CPU implementer : 0x41 CPU architecture: 7 CPU variant : 0x0 CPU part : 0xc07 CPU revision : 4 Hardware : Dummy Virtual Machine Revision : 0000 Serial : 0000000000000000 root@when-the-lie-s-so-big:~# uname -a Linux when-the-lie-s-so-big 3.14.0+ #2465 SMP PREEMPT Tue Apr 8 13:05:11 BST 2014 armv7b GNU/Linux Now, looking at the patch, I think it makes some sense: - Depending on the endianness, we have to test the L_PTE_NONE in one word on the other, and possibly clear L_PTE_VALID - Same for L_PTE_DIRTY, respectively setting L_PTE_RDONLY The commit message looks wrong though, as it mention the PTE storage in memory (which looks completely fine to me, and explain why I was able to boot a guest). As none of my guest RAM is above 4GB IPA, I didn't see the corruption of bit 32 in the PTE (which should have been bit 0, corresponding to L_PTE_VALID). So, provided that the commit message is rewritten to match the what it does, I'm fine with that patch. Thanks, 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