From: Logan Gunthorpe <logang@deltatee.com>
To: Jason Gunthorpe <jgg@mellanox.com>, Christoph Hellwig <hch@lst.de>
Cc: Jerome Glisse <jglisse@redhat.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J . Wysocki" <rafael@kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>,
Christian Koenig <christian.koenig@amd.com>,
Felix Kuehling <Felix.Kuehling@amd.com>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
Joerg Roedel <jroedel@suse.de>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>
Subject: Re: [RFC PATCH 3/5] mm/vma: add support for peer to peer to device vma
Date: Thu, 31 Jan 2019 12:19:31 -0700 [thread overview]
Message-ID: <e4fd743f-61cb-a443-bc53-9a1c036ebe8c@deltatee.com> (raw)
In-Reply-To: <20190131190202.GC7548@mellanox.com>
On 2019-01-31 12:02 p.m., Jason Gunthorpe wrote:
> I still think the right direction is to build on what Logan has done -
> realize that he created a DMA-only SGL - make that a formal type of
> the kernel and provide the right set of APIs to work with this type,
> without being forced to expose struct page.
> Basically invert the API flow - the DMA map would be done close to
> GUP, not buried in the driver. This absolutely doesn't work for every
> flow we have, but it does enable the ones that people seem to care
> about when talking about P2P.
> It also does present a path to solve some cases of the O_DIRECT
> problems if the block stack can develop some way to know if an IO will
> go down a DMA-only IO path or not... This seems less challenging that
> auditing every SGL user for iomem safety??
The DMA-only SGL will work for some use cases, but I think it's going to
be a challenge for others. We care most about NVMe and, therefore, the
block layer.
Given my understanding of the block layer, and it's queuing
infrastructure, I don't think having a DMA-only IO path makes sense. I
think it has to be the same path, but with a special DMA-only bio; and
endpoints would have to indicate support for that bio. I can't say I
have a deep enough understanding of the block layer to know how possible
that would be.
Logan
next prev parent reply other threads:[~2019-01-31 19:19 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-29 17:47 [RFC PATCH 0/5] Device peer to peer (p2p) through vma jglisse
2019-01-29 17:47 ` [RFC PATCH 1/5] pci/p2p: add a function to test peer to peer capability jglisse
2019-01-29 18:24 ` Logan Gunthorpe
2019-01-29 19:44 ` Greg Kroah-Hartman
2019-01-29 19:53 ` Jerome Glisse
2019-01-29 20:44 ` Logan Gunthorpe
2019-01-29 21:00 ` Jerome Glisse
2019-01-29 19:56 ` Alex Deucher
2019-01-29 20:00 ` Jerome Glisse
2019-01-29 20:24 ` Logan Gunthorpe
2019-01-29 21:28 ` Alex Deucher
2019-01-30 10:25 ` Christian König
2019-01-29 17:47 ` [RFC PATCH 2/5] drivers/base: " jglisse
2019-01-29 18:26 ` Logan Gunthorpe
2019-01-29 19:54 ` Jerome Glisse
2019-01-29 19:46 ` Greg Kroah-Hartman
2019-01-29 19:56 ` Jerome Glisse
2019-01-29 17:47 ` [RFC PATCH 3/5] mm/vma: add support for peer to peer to device vma jglisse
2019-01-29 18:36 ` Logan Gunthorpe
2019-01-29 19:11 ` Jerome Glisse
2019-01-29 19:24 ` Logan Gunthorpe
2019-01-29 19:44 ` Jerome Glisse
2019-01-29 20:43 ` Logan Gunthorpe
2019-01-30 7:52 ` Christoph Hellwig
2019-01-29 19:32 ` Jason Gunthorpe
2019-01-29 19:50 ` Jerome Glisse
2019-01-29 20:24 ` Jason Gunthorpe
2019-01-29 20:44 ` Jerome Glisse
2019-01-29 23:02 ` Jason Gunthorpe
2019-01-30 0:08 ` Jerome Glisse
2019-01-30 4:30 ` Jason Gunthorpe
2019-01-30 15:43 ` Jerome Glisse
2019-01-29 20:39 ` Logan Gunthorpe
2019-01-29 20:57 ` Jerome Glisse
2019-01-29 21:30 ` Logan Gunthorpe
2019-01-29 21:50 ` Jerome Glisse
2019-01-29 22:58 ` Logan Gunthorpe
2019-01-29 23:47 ` Jerome Glisse
2019-01-30 1:17 ` Logan Gunthorpe
2019-01-30 2:48 ` Jerome Glisse
2019-01-30 4:18 ` Jason Gunthorpe
2019-01-30 8:00 ` Christoph Hellwig
2019-01-30 15:49 ` Jerome Glisse
2019-01-30 19:06 ` Jason Gunthorpe
[not found] ` <20190130190651.GC17080-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2019-01-30 19:45 ` Logan Gunthorpe
[not found] ` <840256f8-0714-5d7d-e5f5-c96aec5c2c05-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org>
2019-01-30 19:59 ` Jason Gunthorpe
[not found] ` <20190130195900.GG17080-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2019-01-30 21:01 ` Logan Gunthorpe
[not found] ` <35bad6d5-c06b-f2a3-08e6-2ed0197c8691-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org>
2019-01-30 21:50 ` Jason Gunthorpe
[not found] ` <20190130215019.GL17080-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2019-01-30 22:52 ` Logan Gunthorpe
2019-01-30 23:30 ` Jason Gunthorpe
2019-01-31 8:13 ` Christoph Hellwig
2019-01-31 15:37 ` Jerome Glisse
2019-01-31 19:02 ` Jason Gunthorpe
2019-01-31 19:19 ` Logan Gunthorpe [this message]
2019-01-31 19:54 ` Jason Gunthorpe
2019-01-31 19:35 ` Jerome Glisse
2019-01-31 19:44 ` Logan Gunthorpe
2019-01-31 19:58 ` Jason Gunthorpe
2019-01-30 17:17 ` Logan Gunthorpe
[not found] ` <bdf03cd5-f5b1-4b78-a40e-b24024ca8c9f-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org>
2019-01-30 18:56 ` Jason Gunthorpe
[not found] ` <20190130185652.GB17080-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2019-01-30 19:22 ` Jerome Glisse
2019-01-30 19:38 ` Jason Gunthorpe
[not found] ` <20190130193759.GE17080-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2019-01-30 20:00 ` Logan Gunthorpe
2019-01-30 20:11 ` Jason Gunthorpe
2019-01-30 20:43 ` Jerome Glisse
[not found] ` <20190130204332.GF5061-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-01-30 20:50 ` Jason Gunthorpe
2019-01-30 21:45 ` Jerome Glisse
[not found] ` <20190130214525.GG5061-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-01-30 21:56 ` Jason Gunthorpe
2019-01-30 22:30 ` Jerome Glisse
[not found] ` <20190130223027.GH5061-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-01-30 22:33 ` Jason Gunthorpe
2019-01-30 22:47 ` Jerome Glisse
[not found] ` <20190130224705.GI5061-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-01-30 22:51 ` Jason Gunthorpe
2019-01-30 22:58 ` Jerome Glisse
[not found] ` <20190130192234.GD5061-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-01-30 19:52 ` Logan Gunthorpe
2019-01-30 20:35 ` Jerome Glisse
2019-01-29 20:58 ` Jason Gunthorpe
2019-01-30 8:02 ` Christoph Hellwig
2019-01-30 10:33 ` Koenig, Christian
2019-01-30 15:55 ` Jerome Glisse
2019-01-30 17:26 ` Christoph Hellwig
2019-01-30 17:32 ` Logan Gunthorpe
2019-01-30 17:39 ` Jason Gunthorpe
2019-01-30 18:05 ` Jerome Glisse
2019-01-30 17:44 ` Jason Gunthorpe
2019-01-30 18:13 ` Logan Gunthorpe
2019-01-30 18:50 ` Jerome Glisse
2019-01-31 8:02 ` Christoph Hellwig
2019-01-31 15:03 ` Jerome Glisse
2019-01-30 19:19 ` Jason Gunthorpe
[not found] ` <20190130191946.GD17080-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2019-01-30 19:48 ` Logan Gunthorpe
2019-01-30 20:44 ` Jason Gunthorpe
2019-01-31 8:05 ` Christoph Hellwig
2019-01-31 15:11 ` Jerome Glisse
2019-01-29 17:47 ` [RFC PATCH 4/5] mm/hmm: add support for peer to peer to HMM device memory jglisse
2019-01-29 17:47 ` [RFC PATCH 5/5] mm/hmm: add support for peer to peer to special device vma jglisse
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