linux-kernel - Re: [PATCH v2] ARM: mm: support big-endian page tables

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Date:	Tue, 18 Mar 2014 15:35:59 +0800
From:	Jianguo Wu <wujianguo@...wei.com>
To:	<linux@....linux.org.uk>
CC:	Wang Nan <wangnan0@...wei.com>, <gregkh@...uxfoundation.org>,
	<will.deacon@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Li Zefan <lizefan@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] ARM: mm: support big-endian page tables

Hi Russell,

Cloud you please take a look at this?

Thanks!

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@...0M, 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@...0M), 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));
> 	...
> }
> 
> 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@...wei.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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