linux-kernel - Re: [PATCHv2 2/2] arm: Adjust memory boundaries after reservations

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Date:   Fri, 6 Jan 2017 00:41:37 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Laura Abbott <labbott@...hat.com>
Cc:     Nicolas Pitre <nicolas.pitre@...aro.org>,
        Grygorii Strashko <grygorii.strashko@...com>,
        linux-arm-kernel@...ts.infradead.org, lilja.magnus@...il.com,
        festevam@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 2/2] arm: Adjust memory boundaries after reservations

Only comments are to do with the comments...

On Thu, Jan 05, 2017 at 03:01:14PM -0800, Laura Abbott wrote:
> 
> adjust_lowmem_bounds is responsible for setting up the boundary for
> lowmem/hihgmme. This needs to be setup before memblock reservations can

highmem

> occur. At the time memblock reservations can occur, memory can also be
> removed from the system. The lowmem/highmem boundary and end of memory
> may be affected by this but it is currently not recalculated. On some
> systems this may be harmless, on o thers this may result in incorrect

others

> ranges being passed to the main memory allocator. Correct this by
> recalculating the lowmem/highmem boundary after all reservations have
> been made.
> 
> Signed-off-by: Laura Abbott <labbott@...hat.com>
> ---
> v2: Rebased for changes in sanity_check_meminfo cleanup
> ---
>  arch/arm/kernel/setup.c | 8 ++++++++
>  arch/arm/mm/mmu.c       | 9 ++++++---
>  2 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index 8a8051c..4625115 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -1093,8 +1093,16 @@ void __init setup_arch(char **cmdline_p)
>  	setup_dma_zone(mdesc);
>  	xen_early_init();
>  	efi_init();
> +	/*
> +	 * Make sure the calcualtion for lowmem/highmem is set appropriately

calculation

> +	 * before reserving/allocating any mmeory
> +	 */
>  	adjust_lowmem_bounds();
>  	arm_memblock_init(mdesc);
> +	/*
> +	 * Memory may have been removed so recalculate the bounds.
> +	 */

Single line comments should be... /* blah */

> +	adjust_lowmem_bounds();
>  
>  	early_ioremap_reset();
>  
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index ce5123b..7ca6910 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -1157,6 +1157,7 @@ void __init adjust_lowmem_bounds(void)
>  	phys_addr_t memblock_limit = 0;
>  	u64 vmalloc_limit;
>  	struct memblock_region *reg;
> +	phys_addr_t lowmem_limit = 0;
>  
>  	/*
>  	 * Let's use our own (unoptimized) equivalent of __pa() that is
> @@ -1173,14 +1174,14 @@ void __init adjust_lowmem_bounds(void)
>  
>  
>  		if (reg->base < vmalloc_limit) {
> -			if (block_end > arm_lowmem_limit)
> +			if (block_end > lowmem_limit)
>  				/*
>  				 * Compare as u64 to ensure vmalloc_limit does
>  				 * not get truncated. block_end should always
>  				 * fit in phys_addr_t so there should be no
>  				 * issue with assignment.
>  				 */
> -				arm_lowmem_limit = min_t(u64,
> +				lowmem_limit = min_t(u64,
>  							 vmalloc_limit,
>  							 block_end);
>  
> @@ -1201,12 +1202,14 @@ void __init adjust_lowmem_bounds(void)
>  				if (!IS_ALIGNED(block_start, PMD_SIZE))
>  					memblock_limit = block_start;
>  				else if (!IS_ALIGNED(block_end, PMD_SIZE))
> -					memblock_limit = arm_lowmem_limit;
> +					memblock_limit = lowmem_limit;
>  			}
>  
>  		}
>  	}
>  
> +	arm_lowmem_limit = lowmem_limit;
> +
>  	high_memory = __va(arm_lowmem_limit - 1) + 1;
>  
>  	/*
> -- 
> 2.7.4
> 

-- 
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