From: Jianguo Wu <wujianguo@huawei.com>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: Will Deacon <Will.Deacon@arm.com>,
"linux@arm.linux.org.uk" <linux@arm.linux.org.uk>,
Wang Nan <wangnan0@huawei.com>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Li Zefan <lizefan@huawei.com>,
Catalin Marinas <Catalin.Marinas@arm.com>,
Ben Dooks <ben.dooks@codethink.co.uk>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2] ARM: mm: support big-endian page tables
Date: Thu, 17 Apr 2014 12:05:27 +0800 [thread overview]
Message-ID: <534F5307.1030707@huawei.com> (raw)
In-Reply-To: <534E777C.1090605@arm.com>
On 2014/4/16 20:28, Marc Zyngier wrote:
> 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
>>>>>> [<c000f5f0>] (unwind_backtrace+0x0/0x11c) from [<c000cbc4>] (show_stack+0x10/0x14)
>>>>>> [<c000cbc4>] (show_stack+0x10/0x14) from [<c009e448>] (bad_page+0xd4/0x104)
>>>>>> [<c009e448>] (bad_page+0xd4/0x104) from [<c009e520>] (free_pages_prepare+0xa8/0x14c)
>>>>>> [<c009e520>] (free_pages_prepare+0xa8/0x14c) from [<c009f8ec>] (free_hot_cold_page+0x18/0xf0)
>>>>>> [<c009f8ec>] (free_hot_cold_page+0x18/0xf0) from [<c00b5444>] (handle_pte_fault+0xcf4/0xdc8)
>>>>>> [<c00b5444>] (handle_pte_fault+0xcf4/0xdc8) from [<c00b6458>] (handle_mm_fault+0xf4/0x120)
>>>>>> [<c00b6458>] (handle_mm_fault+0xf4/0x120) from [<c0013754>] (do_page_fault+0xfc/0x354)
>>>>>> [<c0013754>] (do_page_fault+0xfc/0x354) from [<c0008400>] (do_DataAbort+0x2c/0x90)
>>>>>> [<c0008400>] (do_DataAbort+0x2c/0x90) from [<c0008fb4>] (__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."
>
OK, I will sent a new version, thanks!
> Cheers,
>
> M.
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prev parent reply other threads:[~2014-04-17 4:06 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-17 7:05 [PATCH v2] ARM: mm: support big-endian page tables Jianguo Wu
2014-03-18 7:35 ` Jianguo Wu
2014-04-14 10:43 ` Will Deacon
2014-04-14 11:14 ` Marc Zyngier
2014-04-16 2:45 ` Jianguo Wu
2014-04-16 12:28 ` Marc Zyngier
2014-04-17 4:05 ` Jianguo Wu [this message]
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