linux-kernel - Re: [PATCH v2 15/22] ARM: mm: use physical addresses in highmem sanity checks

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Message-ID: <alpine.LFD.2.02.1208120029110.5231@xanadu.home>
Date:	Sun, 12 Aug 2012 00:29:54 -0400 (EDT)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Cyril Chemparathy <cyril@...com>
cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	arnd@...db.de, catalin.marinas@....com, grant.likely@...retlab.ca,
	linux@....linux.org.uk, will.deacon@....com,
	Vitaly Andrianov <vitalya@...com>
Subject: Re: [PATCH v2 15/22] ARM: mm: use physical addresses in highmem
 sanity checks

On Fri, 10 Aug 2012, Cyril Chemparathy wrote:

> This patch modifies the highmem sanity checking code to use physical addresses
> instead.  This change eliminates the wrap-around problems associated with the
> original virtual address based checks, and this simplifies the code a bit.
> 
> The one constraint imposed here is that low physical memory must be mapped in
> a monotonically increasing fashion if there are multiple banks of memory,
> i.e., x < y must => pa(x) < pa(y).
> 
> Signed-off-by: Cyril Chemparathy <cyril@...com>
> Signed-off-by: Vitaly Andrianov <vitalya@...com>

Acked-by: Nicolas Pitre <nico@...aro.org>


> ---
>  arch/arm/mm/mmu.c |   22 ++++++++++------------
>  1 file changed, 10 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index 53eeeb8..f764c03 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -895,6 +895,7 @@ phys_addr_t arm_lowmem_limit __initdata = 0;
>  void __init sanity_check_meminfo(void)
>  {
>  	int i, j, highmem = 0;
> +	phys_addr_t vmalloc_limit = __pa(vmalloc_min - 1) + 1;
>  
>  	for (i = 0, j = 0; i < meminfo.nr_banks; i++) {
>  		struct membank *bank = &meminfo.bank[j];
> @@ -904,8 +905,7 @@ void __init sanity_check_meminfo(void)
>  			highmem = 1;
>  
>  #ifdef CONFIG_HIGHMEM
> -		if (__va(bank->start) >= vmalloc_min ||
> -		    __va(bank->start) < (void *)PAGE_OFFSET)
> +		if (bank->start >= vmalloc_limit)
>  			highmem = 1;
>  
>  		bank->highmem = highmem;
> @@ -914,8 +914,8 @@ void __init sanity_check_meminfo(void)
>  		 * Split those memory banks which are partially overlapping
>  		 * the vmalloc area greatly simplifying things later.
>  		 */
> -		if (!highmem && __va(bank->start) < vmalloc_min &&
> -		    bank->size > vmalloc_min - __va(bank->start)) {
> +		if (!highmem && bank->start < vmalloc_limit &&
> +		    bank->size > vmalloc_limit - bank->start) {
>  			if (meminfo.nr_banks >= NR_BANKS) {
>  				printk(KERN_CRIT "NR_BANKS too low, "
>  						 "ignoring high memory\n");
> @@ -924,12 +924,12 @@ void __init sanity_check_meminfo(void)
>  					(meminfo.nr_banks - i) * sizeof(*bank));
>  				meminfo.nr_banks++;
>  				i++;
> -				bank[1].size -= vmalloc_min - __va(bank->start);
> -				bank[1].start = __pa(vmalloc_min - 1) + 1;
> +				bank[1].size -= vmalloc_limit - bank->start;
> +				bank[1].start = vmalloc_limit;
>  				bank[1].highmem = highmem = 1;
>  				j++;
>  			}
> -			bank->size = vmalloc_min - __va(bank->start);
> +			bank->size = vmalloc_limit - bank->start;
>  		}
>  #else
>  		bank->highmem = highmem;
> @@ -949,8 +949,7 @@ void __init sanity_check_meminfo(void)
>  		 * Check whether this memory bank would entirely overlap
>  		 * the vmalloc area.
>  		 */
> -		if (__va(bank->start) >= vmalloc_min ||
> -		    __va(bank->start) < (void *)PAGE_OFFSET) {
> +		if (bank->start >= vmalloc_limit) {
>  			printk(KERN_NOTICE "Ignoring RAM at %.8llx-%.8llx "
>  			       "(vmalloc region overlap).\n",
>  			       (unsigned long long)bank->start,
> @@ -962,9 +961,8 @@ void __init sanity_check_meminfo(void)
>  		 * Check whether this memory bank would partially overlap
>  		 * the vmalloc area.
>  		 */
> -		if (__va(bank->start + bank->size) > vmalloc_min ||
> -		    __va(bank->start + bank->size) < __va(bank->start)) {
> -			unsigned long newsize = vmalloc_min - __va(bank->start);
> +		if (bank->start + bank->size > vmalloc_limit)
> +			unsigned long newsize = vmalloc_limit - bank->start;
>  			printk(KERN_NOTICE "Truncating RAM at %.8llx-%.8llx "
>  			       "to -%.8llx (vmalloc region overlap).\n",
>  			       (unsigned long long)bank->start,
> -- 
> 1.7.9.5
> 
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