From: "joro@8bytes.org" <joro@8bytes.org>
To: Mark Hounschell <markh@compro.net>
Cc: William Davis <wdavis@nvidia.com>,
Bjorn Helgaas <bhelgaas@google.com>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
Terence Ripperda <TRipperda@nvidia.com>,
John Hubbard <jhubbard@nvidia.com>,
"jglisse@redhat.com" <jglisse@redhat.com>,
"konrad.wilk@oracle.com" <konrad.wilk@oracle.com>,
Jonathan Corbet <corbet@lwn.net>,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH v2 4/7] DMA-API: Add dma_(un)map_resource() documentation
Date: Fri, 29 May 2015 10:24:44 +0200 [thread overview]
Message-ID: <20150529082444.GB13130@8bytes.org> (raw)
In-Reply-To: <555CDD6F.40304@compro.net>
On Wed, May 20, 2015 at 03:15:59PM -0400, Mark Hounschell wrote:
> On 05/20/2015 01:30 PM, William Davis wrote:
> >In an IOMMU environment, the DMA ops would be one of the IOMMU
> >implementations, so these APIs would create a mapping for the peer device
> >resource, even if it's on the same bus. Would a transaction targeting that
> >mapping be forwarded upstream until it hits an IOMMU, which would then send
> >the translated request back downstream? Or is my understanding of this
> >configuration incorrect?
> >
>
> It's my understanding of the IOMMU that is lacking here. I have no
> idea if that is actually what would happen. Does it?
On the x86 side at least the IOMMU drivers enable ACS when available,
forcing all perr-to-peer DMA between PCIe devices to go through the
IOMMU. This only works when the peers are in different iommu groups,
though.
Joerg
next prev parent reply other threads:[~2015-05-29 8:24 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-18 18:24 [PATCH v2 0/7] IOMMU/DMA map_resource support for peer-to-peer wdavis
2015-05-18 18:24 ` [PATCH v2 1/7] dma-debug: add checking for map/unmap_resource wdavis
2015-05-18 18:24 ` [PATCH v2 2/7] DMA-API: Introduce dma_(un)map_resource wdavis
2015-05-29 8:16 ` Joerg Roedel
2015-05-18 18:25 ` [PATCH v2 3/7] dma-mapping: pci: add pci_(un)map_resource wdavis
2015-05-18 18:25 ` [PATCH v2 4/7] DMA-API: Add dma_(un)map_resource() documentation wdavis
2015-05-19 23:43 ` Bjorn Helgaas
2015-05-20 12:11 ` Mark Hounschell
2015-05-20 17:30 ` William Davis
2015-05-20 19:15 ` Mark Hounschell
2015-05-20 19:51 ` William Davis
2015-05-20 20:07 ` Mark Hounschell
2015-05-27 18:31 ` William Davis
2015-05-29 8:24 ` joro [this message]
2015-07-07 15:15 ` Bjorn Helgaas
2015-07-07 15:41 ` Alex Williamson
2015-07-07 16:16 ` Bjorn Helgaas
2015-07-07 16:41 ` Alex Williamson
2015-07-07 17:14 ` Mark Hounschell
2015-07-07 17:28 ` Alex Williamson
2015-07-07 19:17 ` Mark Hounschell
2015-07-07 19:54 ` Alex Williamson
2015-07-08 15:11 ` Bjorn Helgaas
2015-07-08 16:40 ` Mark Hounschell
2015-07-09 0:50 ` Rafael J. Wysocki
2015-06-01 21:25 ` Konrad Rzeszutek Wilk
2015-06-02 14:27 ` William Davis
2015-05-18 18:25 ` [PATCH v2 5/7] iommu/amd: Implement (un)map_resource wdavis
2015-05-18 18:25 ` [PATCH v2 6/7] iommu/vt-d: implement (un)map_resource wdavis
2015-05-18 18:25 ` [PATCH v2 7/7] x86: add pci-nommu implementation of map_resource wdavis
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