Re: [PATCH] ARM: mm: support big-endian page tables

[Jianguo Wu <wujianguo@huawei.com>]

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On 2014/2/12 14:54, Jianguo Wu wrote:

> On 2014/2/11 18:40, Ben Dooks wrote:
> 
>> On 11/02/14 09:20, 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 bad pfn:fa442 is not system memory(mem=384M mem=512M@7680M), after debugging,
>>> I find in page fault handler, will get wrong pfn from pte just after set pte,
>>> as follow:
>>> do_anonymous_page()
>>> {
>>>     ...
>>>     set_pte_at(mm, address, page_table, entry);
>>>     
>>>     //debug code
>>>     pfn = pte_pfn(entry);
>>>     pr_info("pfn:0x%lx, pte:0x%llx\n", pfn, pte_val(entry));
>>>
>>>     //read out the pte just set
>>>     new_pte = pte_offset_map(pmd, address);
>>>     new_pfn = pte_pfn(*new_pte);
>>>     pr_info("new pfn:0x%lx, new pte:0x%llx\n", pfn, pte_val(entry));
>>>     ...
>>> }
>>
>> Thanks, must have missed tickling this one.
>>
>>>
>>> pfn:   0x1fa4f5,     pte:0xc00001fa4f575f
>>> new_pfn:0xfa4f5, new_pte:0xc00000fa4f5f5f    //new pfn/pte is wrong.
>>>
>>> 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.
>>>
>>> Signed-off-by: Jianguo Wu <wujianguo@huawei.com>
>>> ---
>>>   arch/arm/mm/proc-v7-3level.S |   10 ++++++++++
>>>   1 files changed, 10 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S
>>> index 6ba4bd9..71b3892 100644
>>> --- a/arch/arm/mm/proc-v7-3level.S
>>> +++ b/arch/arm/mm/proc-v7-3level.S
>>> @@ -65,6 +65,15 @@ ENDPROC(cpu_v7_switch_mm)
>>>    */
>>>   ENTRY(cpu_v7_set_pte_ext)
>>>   #ifdef CONFIG_MMU
>>> +#ifdef CONFIG_CPU_ENDIAN_BE8
>>> +    tst    r3, #L_PTE_VALID
>>> +    beq    1f
>>> +    tst    r2, #1 << (57 - 32)        @ L_PTE_NONE
>>> +    bicne    r3, #L_PTE_VALID
>>> +    bne    1f
>>> +    tst    r2, #1 << (55 - 32)        @ L_PTE_DIRTY
>>> +    orreq    r3, #L_PTE_RDONLY
>>> +#else
>>>       tst    r2, #L_PTE_VALID
>>>       beq    1f
>>>       tst    r3, #1 << (57 - 32)        @ L_PTE_NONE
>>> @@ -72,6 +81,7 @@ ENTRY(cpu_v7_set_pte_ext)
>>>       bne    1f
>>>       tst    r3, #1 << (55 - 32)        @ L_PTE_DIRTY
>>>       orreq    r2, #L_PTE_RDONLY
>>> +#endif
>>>   1:    strd    r2, r3, [r0]
>>>       ALT_SMP(W(nop))
>>>       ALT_UP (mcr    p15, 0, r0, c7, c10, 1)        @ flush_pte
>>> -- 1.7.1
>>
>> If possible can we avoid large #ifdef blocks here?
>>
>> Two ideas are
>>
>> ARM_LE(tst r2, #L_PTE_VALID)
>> ARM_BE(tst r3, #L_PTE_VALID)
>>
>> or change r2, r3 pair to say rlow, rhi and
>>
>> #ifdef  CONFIG_CPU_ENDIAN_BE8
>> #define rlow r3
>> #define rhi r2
>> #else
>> #define rlow r2
>> #define rhi r3
>> #endif
>>
> 
> Hi Ben,
> Thanks for your suggestion, how about this?
> 
> Signed-off-by: Jianguo Wu <wujianguo@huawei.com>
> ---
>  arch/arm/mm/proc-v7-3level.S |   18 +++++++++++++-----
>  1 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S
> index 01a719e..22e3ad6 100644
> --- a/arch/arm/mm/proc-v7-3level.S
> +++ b/arch/arm/mm/proc-v7-3level.S
> @@ -64,6 +64,14 @@ ENTRY(cpu_v7_switch_mm)
>  	mov	pc, lr
>  ENDPROC(cpu_v7_switch_mm)
>  
> +#ifdef __ARMEB__
> +#define rl r3
> +#define rh r2
> +#else
> +#define rl r2
> +#define rh r3
> +#endif
> +
>  /*
>   * cpu_v7_set_pte_ext(ptep, pte)
>   *
> @@ -73,13 +81,13 @@ ENDPROC(cpu_v7_switch_mm)
>   */
>  ENTRY(cpu_v7_set_pte_ext)
>  #ifdef CONFIG_MMU
> -	tst	r2, #L_PTE_VALID
> +	tst	rl, #L_PTE_VALID
>  	beq	1f
> -	tst	r3, #1 << (57 - 32)		@ L_PTE_NONE
> -	bicne	r2, #L_PTE_VALID
> +	tst	rh, #1 << (57 - 32)		@ L_PTE_NONE
> +	bicne	rl, #L_PTE_VALID
>  	bne	1f
> -	tst	r3, #1 << (55 - 32)		@ L_PTE_DIRTY
> -	orreq	r2, #L_PTE_RDONLY
> +	tst	rh, #1 << (55 - 32)		@ L_PTE_DIRTY
> +	orreq	rl, #L_PTE_RDONLY
>  1:	strd	r2, r3, [r0]
>  	ALT_SMP(W(nop))
>  	ALT_UP (mcr	p15, 0, r0, c7, c10, 1)		@ flush_pte



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