From: "Christian König" <christian.koenig@amd.com>
To: Logan Gunthorpe <logang@deltatee.com>,
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
Cc: "Jonathan Corbet" <corbet@lwn.net>,
"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
"Alex Williamson" <alex.williamson@redhat.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Jason Gunthorpe" <jgg@mellanox.com>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Max Gurtovoy" <maxg@mellanox.com>,
"Christoph Hellwig" <hch@lst.de>
Subject: Re: [PATCH v5 06/13] PCI/P2PDMA: Add P2P DMA driver writer's documentation
Date: Fri, 31 Aug 2018 19:38:50 +0200 [thread overview]
Message-ID: <30411655-9b90-749e-857f-318dac7cccbf@amd.com> (raw)
In-Reply-To: <6820d451-9591-1979-00bf-60c65fc4f136@deltatee.com>
Am 31.08.2018 um 17:51 schrieb Logan Gunthorpe:
>
> On 31/08/18 02:08 AM, Christian König wrote:
>>> +One of the biggest issues is that PCI doesn't require forwarding
>>> +transactions between hierarchy domains, and in PCIe, each Root Port
>>> +defines a separate hierarchy domain. To make things worse, there is no
>>> +simple way to determine if a given Root Complex supports this or not.
>>> +(See PCIe r4.0, sec 1.3.1). Therefore, as of this writing, the kernel
>>> +only supports doing P2P when the endpoints involved are all behind the
>>> +same PCI bridge, as such devices are all in the same PCI hierarchy
>>> +domain, and the spec guarantees that all transacations within the
>>> +hierarchy will be routable, but it does not require routing
>>> +between hierarchies.
>> Can we add a kernel command line switch and a whitelist to enable P2P
>> between separate hierarchies?
> In future work, yes. But not for this patchset. This is definitely the
> way I see things going, but we've chosen to start with what we've presented.
Sounds like a plan to me.
If you can separate out adding the detection I can take a look adding
this with my DMA-buf P2P efforts.
Christian.
>
> Logan
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next prev parent reply other threads:[~2018-08-31 17:39 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-30 18:53 [PATCH v5 00/13] Copy Offload in NVMe Fabrics with P2P PCI Memory Logan Gunthorpe
2018-08-30 18:53 ` [PATCH v5 01/13] PCI/P2PDMA: Support peer-to-peer memory Logan Gunthorpe
2018-08-31 8:04 ` Christian König
2018-08-31 15:48 ` Logan Gunthorpe
2018-09-01 8:27 ` Christoph Hellwig
2018-08-31 16:19 ` Jonathan Cameron
2018-08-31 16:26 ` Logan Gunthorpe
2018-08-30 18:53 ` [PATCH v5 02/13] PCI/P2PDMA: Add sysfs group to display p2pmem stats Logan Gunthorpe
2018-08-30 18:53 ` [PATCH v5 03/13] PCI/P2PDMA: Add PCI p2pmem DMA mappings to adjust the bus offset Logan Gunthorpe
2018-08-30 18:53 ` [PATCH v5 04/13] PCI/P2PDMA: Introduce configfs/sysfs enable attribute helpers Logan Gunthorpe
2018-08-30 18:53 ` [PATCH v5 05/13] docs-rst: Add a new directory for PCI documentation Logan Gunthorpe
2018-08-30 18:53 ` [PATCH v5 06/13] PCI/P2PDMA: Add P2P DMA driver writer's documentation Logan Gunthorpe
2018-08-31 0:34 ` Randy Dunlap
2018-08-31 15:44 ` Logan Gunthorpe
2018-08-31 8:08 ` Christian König
2018-08-31 15:51 ` Logan Gunthorpe
2018-08-31 17:38 ` Christian König [this message]
2018-08-31 19:11 ` Logan Gunthorpe
2018-08-30 18:53 ` [PATCH v5 07/13] block: Add PCI P2P flag for request queue and check support for requests Logan Gunthorpe
2018-08-30 19:11 ` Jens Axboe
2018-08-30 19:17 ` Logan Gunthorpe
2018-08-30 19:19 ` Jens Axboe
2018-09-01 8:28 ` Christoph Hellwig
2018-09-03 22:26 ` Logan Gunthorpe
2018-09-05 19:26 ` Jens Axboe
2018-09-05 19:33 ` Logan Gunthorpe
2018-09-05 19:45 ` Jens Axboe
2018-09-05 19:53 ` Logan Gunthorpe
2018-09-05 19:56 ` Christoph Hellwig
2018-09-05 19:54 ` Jens Axboe
2018-09-05 20:11 ` Christoph Hellwig
2018-09-05 20:09 ` Logan Gunthorpe
2018-09-05 20:14 ` Jens Axboe
2018-09-05 20:18 ` Logan Gunthorpe
2018-09-05 20:19 ` Jens Axboe
2018-09-05 20:32 ` Logan Gunthorpe
2018-09-05 20:36 ` Jens Axboe
2018-09-05 21:03 ` Logan Gunthorpe
2018-09-05 21:13 ` Christoph Hellwig
2018-09-05 21:18 ` Jens Axboe
2018-09-10 16:41 ` Christoph Hellwig
2018-09-10 18:11 ` Logan Gunthorpe
2018-09-11 7:10 ` Christoph Hellwig
2018-08-30 18:53 ` [PATCH v5 08/13] IB/core: Ensure we map P2P memory correctly in rdma_rw_ctx_[init|destroy]() Logan Gunthorpe
2018-08-31 0:18 ` Sagi Grimberg
2018-08-30 18:53 ` [PATCH v5 09/13] nvme-pci: Use PCI p2pmem subsystem to manage the CMB Logan Gunthorpe
2018-08-30 18:53 ` [PATCH v5 10/13] nvme-pci: Add support for P2P memory in requests Logan Gunthorpe
2018-09-04 15:16 ` Jason Gunthorpe
2018-09-04 15:47 ` Logan Gunthorpe
2018-09-05 19:22 ` Christoph Hellwig
2018-08-30 18:53 ` [PATCH v5 11/13] nvme-pci: Add a quirk for a pseudo CMB Logan Gunthorpe
2018-08-30 18:53 ` [PATCH v5 12/13] nvmet: Introduce helper functions to allocate and free request SGLs Logan Gunthorpe
2018-08-31 0:14 ` Sagi Grimberg
2018-08-30 18:53 ` [PATCH v5 13/13] nvmet: Optionally use PCI P2P memory Logan Gunthorpe
2018-08-31 0:25 ` Sagi Grimberg
2018-08-31 15:41 ` Logan Gunthorpe
2018-08-30 19:20 ` [PATCH v5 00/13] Copy Offload in NVMe Fabrics with P2P PCI Memory Jerome Glisse
2018-08-30 19:30 ` Logan Gunthorpe
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