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Subject: Re: [PATCH for-next 2/4] RDMA/hns: Add IOMMU enable support in hip08
To: Jason Gunthorpe <jgg@ziepe.ca>
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From: "Wei Hu (Xavier)" <xavier.huwei@huawei.com>
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Date: Thu, 9 Nov 2017 09:30:08 +0800
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On 2017/11/7 23:48, Jason Gunthorpe wrote:
> On Tue, Nov 07, 2017 at 10:45:29AM +0800, Wei Hu (Xavier) wrote:
>
>>     We reconstruct the code as below:
>>             It replaces dma_alloc_coherent with __get_free_pages and
>> dma_map_single functions. So, we can vmap serveral ptrs returned by
>> __get_free_pages, right?
> Can't you just use vmalloc and dma_map that? Other drivers follow that
> approach..
>
> However, dma_alloc_coherent and dma_map_single are not the same
> thing. You can't touch the vmap memory once you call dma_map unless
> the driver also includes dma cache flushing calls in all the right
> places.
>
> The difference is that alloc_coherent will return non-cachable memory
> if necessary, while get_free_pages does not.
>
> Jason

Hi, Jason
    Thanks for your suggestion.
    We will fix it.
	
    Regards
Wei Hu

>
> .
>