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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: Fri, 13 Mar 2020 04:21:39 -0700	[thread overview]
Message-ID: <20200313112139.GA4913@infradead.org> (raw)
In-Reply-To: <20200312141928.GK31668@ziepe.ca>

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.

> I haven't used bio_vecs before, do they support chaining like SGL so
> they can be very big? RDMA dma maps gigabytes of memory

bio_vecs itself don't have the chaining, but the bios build around them
do.  But each entry can map a huge pile.  If needed we could use the
same chaining scheme we use for scatterlists for bio_vecs as well, but
lets see if we really end up needing that.

> So I'm guessing the path forward is something like
> 
>  - Add some generic dma_sg data structure and helper
>  - Add dma mapping code to go from pages to dma_sg

That has been on my todo list for a while.  All the DMA consolidatation
is to prepare for that and we're finally getting close.
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  parent reply	other threads:[~2020-03-16 14:18 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 [this message]
2020-03-13 13:33                 ` Christian König
     [not found]                 ` <20200313121742.GZ31668@ziepe.ca>
2020-03-16  8:56                   ` Christoph Hellwig
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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