From: Dan Williams <dan.j.williams@intel.com>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: "Jens Axboe" <axboe@kernel.dk>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"Alex Williamson" <alex.williamson@redhat.com>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
"Sinan Kaya" <okaya@codeaurora.org>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Jason Gunthorpe" <jgg@mellanox.com>,
"Bjorn Helgaas" <helgaas@kernel.org>,
"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Max Gurtovoy" <maxg@mellanox.com>,
"Keith Busch" <keith.busch@intel.com>,
"Christoph Hellwig" <hch@lst.de>
Subject: Re: [PATCH v3 01/11] PCI/P2PDMA: Support peer-to-peer memory
Date: Wed, 14 Mar 2018 12:28:04 -0700 [thread overview]
Message-ID: <CAPcyv4g-A6fqdTahxX=aONSCgp1eEvBb=ZVMzbZUWUDmqBbj7Q@mail.gmail.com> (raw)
In-Reply-To: <b75e83ad-bb83-1f8d-1751-0989cc2493f1@deltatee.com>
On Wed, Mar 14, 2018 at 12:03 PM, Logan Gunthorpe <logang@deltatee.com> wrote:
>
>
> On 14/03/18 12:51 PM, Bjorn Helgaas wrote:
>> You are focused on PCIe systems, and in those systems, most topologies
>> do have an upstream switch, which means two upstream bridges. I'm
>> trying to remove that assumption because I don't think there's a
>> requirement for it in the spec. Enforcing this assumption complicates
>> the code and makes it harder to understand because the reader says
>> "huh, I know peer-to-peer DMA should work inside any PCI hierarchy*,
>> so why do we need these two bridges?"
>
> Yes, as I've said, we focused on being behind a single PCIe Switch
> because it's easier and vaguely safer (we *know* switches will work but
> other types of topology we have to assume will work based on the spec).
> Also, I have my doubts that anyone will ever have a use for this with
> non-PCIe devices.
P2P over PCI/PCI-X is quite common in devices like raid controllers.
It would be useful if those configurations were not left behind so
that Linux could feasibly deploy offload code to a controller in the
PCI domain.
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next prev parent reply other threads:[~2018-03-14 19:21 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-12 19:35 [PATCH v3 00/11] Copy Offload in NVMe Fabrics with P2P PCI Memory Logan Gunthorpe
2018-03-12 19:35 ` [PATCH v3 01/11] PCI/P2PDMA: Support peer-to-peer memory Logan Gunthorpe
2018-03-13 3:28 ` Sinan Kaya
2018-03-13 16:43 ` Logan Gunthorpe
2018-03-13 17:49 ` Sinan Kaya
2018-03-13 18:44 ` Logan Gunthorpe
2018-03-13 19:10 ` Sinan Kaya
2018-03-13 19:19 ` Logan Gunthorpe
2018-03-13 19:53 ` Sinan Kaya
2018-03-13 20:46 ` Logan Gunthorpe
2018-03-13 21:22 ` Sinan Kaya
2018-03-13 22:00 ` Logan Gunthorpe
2018-03-13 22:29 ` Sinan Kaya
2018-03-13 22:45 ` Stephen Bates
2018-03-13 22:48 ` Logan Gunthorpe
2018-03-13 23:19 ` Sinan Kaya
2018-03-13 23:45 ` Logan Gunthorpe
2018-03-14 12:16 ` David Laight
2018-03-14 16:23 ` Logan Gunthorpe
2018-03-13 22:31 ` Stephen Bates
2018-03-13 23:08 ` Bjorn Helgaas
2018-03-13 23:21 ` Logan Gunthorpe
2018-03-14 2:56 ` Bjorn Helgaas
2018-03-14 14:05 ` Stephen Bates
2018-03-14 16:17 ` Logan Gunthorpe
2018-03-14 18:51 ` Bjorn Helgaas
2018-03-14 19:03 ` Logan Gunthorpe
2018-03-14 19:28 ` Dan Williams [this message]
2018-03-14 19:30 ` Logan Gunthorpe
2018-03-14 19:34 ` Stephen Bates
2018-03-15 4:00 ` Martin K. Petersen
2018-03-15 4:30 ` Dan Williams
2018-03-22 22:57 ` Stephen Bates
2018-03-23 21:50 ` Bjorn Helgaas
2018-03-23 21:59 ` Logan Gunthorpe
2018-03-24 3:49 ` Bjorn Helgaas
2018-03-24 15:28 ` Stephen Bates
2018-03-26 15:43 ` Logan Gunthorpe
2018-03-26 11:11 ` Jonathan Cameron
2018-03-26 14:01 ` Bjorn Helgaas
2018-03-26 15:46 ` Logan Gunthorpe
2018-03-27 8:47 ` Jonathan Cameron
2018-03-27 15:37 ` Logan Gunthorpe
2018-04-13 21:56 ` Stephen Bates
2018-03-26 16:41 ` Jason Gunthorpe
2018-03-26 17:30 ` Logan Gunthorpe
2018-03-26 19:35 ` Jason Gunthorpe
2018-03-26 20:42 ` Logan Gunthorpe
2018-03-13 18:40 ` Logan Gunthorpe
2018-03-12 19:35 ` [PATCH v3 02/11] PCI/P2PDMA: Add sysfs group to display p2pmem stats Logan Gunthorpe
2018-03-12 19:35 ` [PATCH v3 03/11] PCI/P2PDMA: Add PCI p2pmem dma mappings to adjust the bus offset Logan Gunthorpe
2018-03-12 19:35 ` [PATCH v3 04/11] PCI/P2PDMA: Clear ACS P2P flags for all devices behind switches Logan Gunthorpe
2018-03-12 19:35 ` [PATCH v3 05/11] PCI/P2PDMA: Add P2P DMA driver writer's documentation Logan Gunthorpe
2018-03-12 19:41 ` Jonathan Corbet
2018-03-12 21:18 ` Logan Gunthorpe
2018-03-12 19:35 ` [PATCH v3 06/11] block: Introduce PCI P2P flags for request and request queue Logan Gunthorpe
2018-03-21 9:27 ` Christoph Hellwig
2018-03-12 19:35 ` [PATCH v3 07/11] IB/core: Ensure we map P2P memory correctly in rdma_rw_ctx_[init|destroy]() Logan Gunthorpe
2018-03-21 9:27 ` Christoph Hellwig
2018-03-12 19:35 ` [PATCH v3 08/11] nvme-pci: Use PCI p2pmem subsystem to manage the CMB Logan Gunthorpe
2018-03-13 1:55 ` Sinan Kaya
2018-03-13 1:58 ` Sinan Kaya
2018-03-12 19:35 ` [PATCH v3 09/11] nvme-pci: Add support for P2P memory in requests Logan Gunthorpe
2018-03-21 9:23 ` Christoph Hellwig
2018-03-12 19:35 ` [PATCH v3 10/11] nvme-pci: Add a quirk for a pseudo CMB Logan Gunthorpe
2018-03-12 19:35 ` [PATCH v3 11/11] nvmet: Optionally use PCI P2P memory Logan Gunthorpe
2018-03-21 9:27 ` Christoph Hellwig
2018-03-21 16:52 ` Logan Gunthorpe
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