From: "hch@lst.de" <hch@lst.de>
To: christian.koenig@amd.com
Cc: Thomas Hellstrom <thellstrom@vmware.com>,
"hch@lst.de" <hch@lst.de>, "jgg@ziepe.ca" <jgg@ziepe.ca>,
"syeh@vmware.com" <syeh@vmware.com>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"daniel.vetter@ffwll.ch" <daniel.vetter@ffwll.ch>,
"jian.xu.zheng@intel.com" <jian.xu.zheng@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"sakari.ailus@linux.intel.com" <sakari.ailus@linux.intel.com>,
"bingbu.cao@intel.com" <bingbu.cao@intel.com>,
"yong.zhi@intel.com" <yong.zhi@intel.com>,
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Subject: Re: [PATCH] lib/scatterlist: Provide a DMA page iterator
Date: Tue, 15 Jan 2019 16:20:29 +0100 [thread overview]
Message-ID: <20190115152029.GB2325@lst.de> (raw)
In-Reply-To: <2b440a3b-ed2f-8fd6-a21e-97ca0b2f5db9@gmail.com>
On Tue, Jan 15, 2019 at 03:24:55PM +0100, Christian König wrote:
> Yeah, indeed. Bounce buffers are an absolute no-go for GPUs.
>
> If the DMA API finds that a piece of memory is not directly accessible by
> the GPU we need to return an error and not try to use bounce buffers behind
> the surface.
>
> That is something which always annoyed me with the DMA API, which is
> otherwise rather cleanly defined.
That is exactly what I want to fix with my series to make
DMA_ATTR_NON_CONSISTENT more useful and always available:
https://lists.linuxfoundation.org/pipermail/iommu/2018-December/031985.html
With that you allocate the memory using dma_alloc_attrs with
DMA_ATTR_NON_CONSISTENT, and use dma_sync_single_* to transfer
ownership to the cpu and back to the device, with a gurantee that
there won't be any bouncing. So far the interest by the parties that
requested the feature has been rather lacklustre, though.
next prev parent reply other threads:[~2019-01-15 15:20 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-04 22:35 [PATCH] lib/scatterlist: Provide a DMA page iterator Jason Gunthorpe
2019-01-05 2:37 ` kbuild test robot
2019-01-05 3:21 ` Jason Gunthorpe
2019-01-10 23:42 ` Jason Gunthorpe
2019-01-14 9:48 ` Christoph Hellwig
2019-01-15 14:17 ` Thomas Hellstrom
2019-01-15 14:24 ` Christian König
2019-01-15 15:20 ` hch [this message]
2019-01-15 18:03 ` Thomas Hellstrom
2019-01-15 18:31 ` hch
2019-01-15 19:13 ` Koenig, Christian
2019-01-15 20:58 ` hch
2019-01-16 7:09 ` Thomas Hellstrom
2019-01-16 7:28 ` Koenig, Christian
2019-01-16 10:14 ` Daniel Vetter
2019-01-16 16:06 ` hch
2019-01-16 16:36 ` Daniel Stone
2019-01-15 21:25 ` Jason Gunthorpe
2019-01-16 10:40 ` Christian König
2019-01-16 16:11 ` hch
2019-01-16 17:24 ` Jason Gunthorpe
2019-01-17 9:30 ` hch
2019-01-17 10:47 ` Thomas Hellstrom
2019-01-17 15:54 ` Jason Gunthorpe
2019-01-12 18:27 ` Shiraz Saleem
2019-01-12 18:37 ` Jason Gunthorpe
2019-01-12 19:03 ` Shiraz Saleem
2019-01-14 9:46 ` Christoph Hellwig
2019-01-14 22:16 ` Jason Gunthorpe
2019-01-16 17:32 ` Shiraz Saleem
2019-02-07 23:23 ` Sakari Ailus
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