From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: To: =?UTF-8?Q?Christian_K=c3=b6nig?= , Bjorn Helgaas , Alex Williamson Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-nvme@lists.infradead.org, linux-rdma@vger.kernel.org, linux-nvdimm@lists.01.org, linux-block@vger.kernel.org, Stephen Bates , Christoph Hellwig , Jens Axboe , Keith Busch , Sagi Grimberg , Bjorn Helgaas , Jason Gunthorpe , Max Gurtovoy , Dan Williams , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Benjamin Herrenschmidt References: <20180423233046.21476-1-logang@deltatee.com> <20180423233046.21476-5-logang@deltatee.com> <20180507231306.GG161390@bhelgaas-glaptop.roam.corp.google.com> <0b4183ef-e720-204b-9e85-b9eaf7a4136a@deltatee.com> From: Logan Gunthorpe Message-ID: <3584a6ac-95c7-5d23-1859-aee30605776e@deltatee.com> Date: Tue, 8 May 2018 13:13:40 -0600 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Subject: Re: [PATCH v4 04/14] PCI/P2PDMA: Clear ACS P2P flags for all devices behind switches List-ID: 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