Re: [RFC PATCH 1/3] mm/cma: Move dma contiguous changes into a seperate config

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

Marek Szyprowski <m.szyprowski@samsung.com> writes:

> Hello,
>
> On 6/24/2013 10:25 AM, Aneesh Kumar K.V wrote:
>> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
>>
>> We want to use CMA for allocating hash page table and real mode area for
>> PPC64. Hence move DMA contiguous related changes into a seperate config
>> so that ppc64 can enable CMA without requiring DMA contiguous.
>>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
>
> It's nice to see that CMA is gaining another client in mainline Linux 
> kernel.
> I also like the idea of adding CONFIG_DMA_CMA for DMA-mapping related CMA
> use to let others to use alloc_contig_range() interface.
>
> However I noticed that You have almost copied the whole drivers/base.c for
> separate use with PPC64 KVM. Is this really necessary? I think it should be
> possible to isolate some common code, which plays with contiguous region
> management and use it for both alloc_contig_range() clients (dma-mapping and
> ppc64 kvm).
>

One of the reason for having book3s_hv_cma.c is that few specifics vary
between dma contiguous. We have different alignment needs. Also i will be
switching the allocation to 256K chunks, not page size, in the next
update. It is also not large code duplication. I will post V2 soon and
may be we can see if it is worth consolidating.

-aneesh