From: Jason Gunthorpe <jgg@ziepe.ca>
To: "Wei Hu (Xavier)" <xavier.huwei@huawei.com>
Cc: Robin Murphy <robin.murphy@arm.com>,
Leon Romanovsky <leon@kernel.org>,
shaobo.xu@intel.com, xavier.huwei@tom.com, lijun_nudt@163.com,
oulijun@huawei.com, linux-rdma@vger.kernel.org,
charles.chenxin@huawei.com, linuxarm@huawei.com,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, dledford@redhat.com, liuyixian@huawei.com,
zhangxiping3@huawei.com, shaoboxu@tom.com
Subject: Re: [PATCH for-next 2/4] RDMA/hns: Add IOMMU enable support in hip08
Date: Tue, 7 Nov 2017 08:48:38 -0700 [thread overview]
Message-ID: <20171107154838.GC21466@ziepe.ca> (raw)
In-Reply-To: <5A011E49.6060407@huawei.com>
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
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next prev parent reply other threads:[~2017-11-07 15:48 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1506763741-81429-1-git-send-email-xavier.huwei@huawei.com>
[not found] ` <1506763741-81429-3-git-send-email-xavier.huwei@huawei.com>
[not found] ` <20170930161023.GI2965@mtr-leonro.local>
2017-10-12 12:31 ` [PATCH for-next 2/4] RDMA/hns: Add IOMMU enable support in hip08 Wei Hu (Xavier)
2017-10-12 12:59 ` Robin Murphy
2017-11-01 7:46 ` Wei Hu (Xavier)
2017-11-01 12:26 ` Robin Murphy
2017-11-07 2:45 ` Wei Hu (Xavier)
2017-11-07 6:32 ` Leon Romanovsky
2017-11-09 1:17 ` Wei Hu (Xavier)
2017-11-07 15:48 ` Jason Gunthorpe [this message]
2017-11-07 15:58 ` Christoph Hellwig
2017-11-07 16:03 ` Jason Gunthorpe
2017-11-09 1:26 ` Wei Hu (Xavier)
2017-11-09 1:30 ` Wei Hu (Xavier)
2017-11-09 1:36 ` Wei Hu (Xavier)
2017-10-12 14:54 ` Leon Romanovsky
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