linux-kernel - Re: [PATCH 14/24] mm/lib/swiotlb: Use memblock apis for early memory allocations

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Date:	Sat, 9 Nov 2013 14:07:41 -0500
From:	Santosh Shilimkar <santosh.shilimkar@...com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	<tj@...nel.org>, <linux-kernel@...r.kernel.org>,
	<linux-mm@...ck.org>, <linux-arm-kernel@...ts.infradead.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 14/24] mm/lib/swiotlb: Use memblock apis for early memory
 allocations

On Saturday 09 November 2013 11:55 AM, Konrad Rzeszutek Wilk wrote:
> Santosh Shilimkar <santosh.shilimkar@...com> wrote:
>> Switch to memblock interfaces for early memory allocator instead of
>> bootmem allocator. No functional change in beahvior than what it is
>> in current code from bootmem users points of view.
>>
>> Archs already converted to NO_BOOTMEM now directly use memblock
>> interfaces instead of bootmem wrappers build on top of memblock. And
>> the
>> archs which still uses bootmem, these new apis just fallback to exiting
>> bootmem APIs.
>>
>> Cc: Yinghai Lu <yinghai@...nel.org>
>> Cc: Tejun Heo <tj@...nel.org>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
>>
>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@...com>
>> ---
>> lib/swiotlb.c |   36 +++++++++++++++++++++---------------
>> 1 file changed, 21 insertions(+), 15 deletions(-)
>>
>> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
>> index 4e8686c..78ac01a 100644
>> --- a/lib/swiotlb.c
>> +++ b/lib/swiotlb.c
>> @@ -169,8 +169,9 @@ int __init swiotlb_init_with_tbl(char *tlb,
>> unsigned long nslabs, int verbose)
>> 	/*
>> 	 * Get the overflow emergency buffer
>> 	 */
>> -	v_overflow_buffer = alloc_bootmem_low_pages_nopanic(
>> -						PAGE_ALIGN(io_tlb_overflow));
>> +	v_overflow_buffer = memblock_virt_alloc_align_nopanic(
>> +						PAGE_ALIGN(io_tlb_overflow),
>> +						PAGE_SIZE);
> 
> Does this guarantee that the pages will be allocated below 4GB?
> 
Yes. The memblock layer still allocates memory from lowmem. As I
mentioned, there is no change in the behavior than what is today
apart from just the interface change.

Regards,
Santosh

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