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Message-ID: <3584a6ac-95c7-5d23-1859-aee30605776e@deltatee.com>
Date: Tue, 8 May 2018 13:13:40 -0600
From: Logan Gunthorpe <logang@...tatee.com>
To: Christian König <christian.koenig@....com>,
Bjorn Helgaas <helgaas@...nel.org>,
Alex Williamson <alex.williamson@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
linux-nvme@...ts.infradead.org, linux-rdma@...r.kernel.org,
linux-nvdimm@...ts.01.org, linux-block@...r.kernel.org,
Stephen Bates <sbates@...thlin.com>,
Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
Keith Busch <keith.busch@...el.com>,
Sagi Grimberg <sagi@...mberg.me>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Jason Gunthorpe <jgg@...lanox.com>,
Max Gurtovoy <maxg@...lanox.com>,
Dan Williams <dan.j.williams@...el.com>,
Jérôme Glisse <jglisse@...hat.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH v4 04/14] PCI/P2PDMA: Clear ACS P2P flags for all devices
behind switches
On 08/05/18 10:50 AM, Christian König wrote:
> E.g. transactions are initially send to the root complex for
> translation, that's for sure. But at least for AMD GPUs the root complex
> answers with the translated address which is then cached in the device.
>
> So further transactions for the same address range then go directly to
> the destination.
Sounds like you are referring to Address Translation Services (ATS).
This is quite separate from ACS and, to my knowledge, isn't widely
supported by switch hardware.
Logan
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