[PATCH 1/2] mm: cma: adjust address limit to avoid hitting low/high memory boundary

[Michal Nazarewicz]

On Thu, Aug 21 2014, Marek Szyprowski <m.szyprowski at samsung.com> wrote:
> Automatically allocated regions should not cross low/high memory boundary,
> because such regions cannot be later correctly initialized due to spanning
> across two memory zones. This patch adds a check for this case and a simple
> code for moving region to low memory if automatically selected address might
> not fit completely into high memory.
>
> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>

Acked-by: Michal Nazarewicz <mina86 at mina86.com>

> ---
>  mm/cma.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>
> diff --git a/mm/cma.c b/mm/cma.c
> index c17751c0dcaf..4acc6aa4a086 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -32,6 +32,7 @@
>  #include <linux/slab.h>
>  #include <linux/log2.h>
>  #include <linux/cma.h>
> +#include <linux/highmem.h>
>  
>  struct cma {
>  	unsigned long	base_pfn;
> @@ -163,6 +164,8 @@ int __init cma_declare_contiguous(phys_addr_t base,
>  			bool fixed, struct cma **res_cma)
>  {
>  	struct cma *cma;
> +	phys_addr_t memblock_end = memblock_end_of_DRAM();
> +	phys_addr_t highmem_start = __pa(high_memory);
>  	int ret = 0;
>  
>  	pr_debug("%s(size %lx, base %08lx, limit %08lx alignment %08lx)\n",
> @@ -196,6 +199,24 @@ int __init cma_declare_contiguous(phys_addr_t base,
>  	if (!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit))
>  		return -EINVAL;
>  
> +	/*
> +	 * adjust limit to avoid crossing low/high memory boundary for
> +	 * automatically allocated regions
> +	 */
> +	if (((limit == 0 || limit > memblock_end) &&
> +	     (memblock_end - size < highmem_start &&
> +	      memblock_end > highmem_start)) ||
> +	    (!fixed && limit > highmem_start && limit - size < highmem_start)) {
> +		limit = highmem_start;
> +	}
> +
> +	if (fixed && base < highmem_start && base+size > highmem_start) {
> +		ret = -EINVAL;
> +		pr_err("Region at %08lx defined on low/high memory boundary (%08lx)\n",
> +			(unsigned long)base, (unsigned long)highmem_start);
> +		goto err;
> +	}
> +
>  	/* Reserve memory */
>  	if (base && fixed) {
>  		if (memblock_is_region_reserved(base, size) ||
> -- 
> 1.9.2
>

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +--<mpn at google.com>--<xmpp:mina86 at jabber.org>--ooO--(_)--Ooo--