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From: Christoph Hellwig <hch@infradead.org>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: David1.Zhou@amd.com, "Logan Gunthorpe" <logang@deltatee.com>,
	intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	"Christoph Hellwig" <hch@infradead.org>,
	linaro-mm-sig@lists.linaro.org,
	"Christian König" <christian.koenig@amd.com>,
	linux-media@vger.kernel.org
Subject: Re: [Intel-gfx] [PATCH 1/6] lib/scatterlist: add sg_set_dma_addr() function
Date: Mon, 16 Mar 2020 01:56:42 -0700	[thread overview]
Message-ID: <20200316085642.GC1831@infradead.org> (raw)
In-Reply-To: <20200313121742.GZ31668@ziepe.ca>

On Fri, Mar 13, 2020 at 09:17:42AM -0300, Jason Gunthorpe wrote:
> On Fri, Mar 13, 2020 at 04:21:39AM -0700, Christoph Hellwig wrote:
> > On Thu, Mar 12, 2020 at 11:19:28AM -0300, Jason Gunthorpe wrote:
> > > The non-page scatterlist is also a big concern for RDMA as we have
> > > drivers that want the page list, so even if we did as this series
> > > contemplates I'd have still have to split the drivers and create the
> > > notion of a dma-only SGL.
> > 
> > The drivers I looked at want a list of IOVA address, aligned to the
> > device "page size".  What other data do drivers want?  Execept for the
> > software protocol stack drivers, which of couse need pages for the
> > stack futher down.
> 
> In principle it is possible to have just an aligned page list -
> however the page size is variable, following certain rules, and today
> the drivers still determine the correct page size largely on their
> own.  
> 
> Some progress was made recently to consolidate this, but more is
> needed.
> 
> If the common code doesn't know the device page size in advance then
> today's approach of sending largest possible dma mapped SGLs into the
> device driver is best. The driver only has to do splitting.

The point was that drivers don't need pages, drivers need IOVAs.  In
what form they are stuffed into the hardware is the drivers problem.
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  parent reply	other threads:[~2020-03-16 14:17 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-11 13:51 [Intel-gfx] P2P for DMA-buf Christian König
2020-03-11 13:51 ` [Intel-gfx] [PATCH 1/6] lib/scatterlist: add sg_set_dma_addr() function Christian König
2020-03-11 15:28   ` Christoph Hellwig
2020-03-12 10:14     ` Christian König
2020-03-12 10:19       ` Christoph Hellwig
2020-03-12 10:31         ` Christian König
2020-03-12 10:47           ` Christoph Hellwig
2020-03-12 11:02             ` Christian König
     [not found]             ` <20200312141928.GK31668@ziepe.ca>
2020-03-12 15:39               ` Christian König
2020-03-12 16:13               ` Logan Gunthorpe
2020-03-13 11:21               ` Christoph Hellwig
2020-03-13 13:33                 ` Christian König
     [not found]                 ` <20200313121742.GZ31668@ziepe.ca>
2020-03-16  8:56                   ` Christoph Hellwig [this message]
2020-03-16  9:41                     ` Christian König
2020-03-16  9:52                       ` Christoph Hellwig
2020-03-11 13:51 ` [Intel-gfx] [PATCH 2/6] dma-buf: add peer2peer flag Christian König
2020-03-11 13:51 ` [Intel-gfx] [PATCH 3/6] drm/amdgpu: note that we can handle peer2peer DMA-buf Christian König
2020-03-11 13:51 ` [Intel-gfx] [PATCH 4/6] drm/amdgpu: add checks if DMA-buf P2P is supported Christian König
     [not found]   ` <20200311140415.GB31668@ziepe.ca>
2020-03-11 14:33     ` Christian König
     [not found]       ` <20200311143835.GD31668@ziepe.ca>
2020-03-11 14:43         ` Christian König
2020-03-11 13:51 ` [Intel-gfx] [PATCH 5/6] drm/amdgpu: add support for exporting VRAM using DMA-buf v2 Christian König
2020-03-11 15:08   ` Alex Deucher
2020-03-11 13:51 ` [Intel-gfx] [PATCH 6/6] drm/amdgpu: improve amdgpu_gem_info debugfs file Christian König
2020-03-11 18:09 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for series starting with [1/6] lib/scatterlist: add sg_set_dma_addr() function Patchwork
2020-03-11 18:34 ` [Intel-gfx] ✗ Fi.CI.BAT: failure " Patchwork

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