From: Logan Gunthorpe <logang@deltatee.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Bjorn Helgaas <helgaas@kernel.org>,
Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
"James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Jens Axboe <axboe@kernel.dk>,
Steve Wise <swise@opengridcomputing.com>,
Stephen Bates <sbates@raithlin.com>,
Max Gurtovoy <maxg@mellanox.com>,
Keith Busch <keith.busch@intel.com>,
linux-pci@vger.kernel.org,
linux-scsi <linux-scsi@vger.kernel.org>,
linux-nvme@lists.infradead.org, linux-rdma@vger.kernel.org,
linux-nvdimm <linux-nvdimm@ml01.01.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Jerome Glisse <jglisse@redhat.com>
Subject: Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory
Date: Tue, 18 Apr 2017 16:56:20 -0600 [thread overview]
Message-ID: <462e318b-bcb8-7031-5b25-2c245086e077@deltatee.com> (raw)
In-Reply-To: <CAPcyv4jArrOBBih5jOU5wrC2imdo9VPzuQpfzepP3_QEwM-33g@mail.gmail.com>
On 18/04/17 04:50 PM, Dan Williams wrote:
> On Tue, Apr 18, 2017 at 3:48 PM, Logan Gunthorpe <logang@deltatee.com> wrote:
>>
>>
>> On 18/04/17 04:28 PM, Dan Williams wrote:
>>> Unlike the pci bus address offset case which I think is fundamental to
>>> support since shipping archs do this today, I think it is ok to say
>>> p2p is restricted to a single sgl that gets to talk to host memory or
>>> a single device. That said, what's wrong with a p2p aware map_sg
>>> implementation calling up to the host memory map_sg implementation on
>>> a per sgl basis?
>>
>> I think Ben said they need mixed sgls and that is where this gets messy.
>> I think I'd prefer this too given trying to enforce all sgs in a list to
>> be one type or another could be quite difficult given the state of the
>> scatterlist code.
>>
>>>> Also, what happens if p2p pages end up getting passed to a device that
>>>> doesn't have the injected dma_ops?
>>>
>>> This goes back to limiting p2p to a single pci host bridge. If the p2p
>>> capability is coordinated with the bridge rather than between the
>>> individual devices then we have a central point to catch this case.
>>
>> Not really relevant. If these pages get to userspace (as people seem
>> keen on doing) or a less than careful kernel driver they could easily
>> get into the dma_map calls of devices that aren't even pci related (via
>> an O_DIRECT operation on an incorrect file or something). The common
>> code must reject these and can't rely on an injected dma op.
>
> No, we can't do that at get_user_pages() time, it will always need to
> be up to the device driver to fail dma that it can't perform.
I'm not sure I follow -- are you agreeing with me? The dma_map_* needs
to fail for any dma it cannot perform. Which means either all dma_ops
providers need to be p2p aware or this logic has to be in dma_map_*
itself. My point being: you can't rely on an injected dma_op for some
devices to handle the fail case globally.
next prev parent reply other threads:[~2017-04-18 22:56 UTC|newest]
Thread overview: 105+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-16 15:44 [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams
2017-04-16 16:47 ` Logan Gunthorpe
2017-04-16 22:32 ` Benjamin Herrenschmidt
2017-04-17 5:13 ` Logan Gunthorpe
2017-04-17 7:20 ` Benjamin Herrenschmidt
2017-04-17 16:52 ` Logan Gunthorpe
2017-04-17 17:04 ` Dan Williams
2017-04-18 5:22 ` Logan Gunthorpe
2017-04-17 18:04 ` Jerome Glisse
2017-04-18 6:14 ` Logan Gunthorpe
2017-04-17 21:11 ` Benjamin Herrenschmidt
2017-04-18 5:43 ` Logan Gunthorpe
2017-04-18 6:29 ` Benjamin Herrenschmidt
2017-04-16 22:23 ` Benjamin Herrenschmidt
2017-04-18 16:45 ` Jason Gunthorpe
2017-04-18 17:27 ` Dan Williams
2017-04-18 18:00 ` Jason Gunthorpe
2017-04-18 18:34 ` Dan Williams
2017-04-19 1:13 ` Benjamin Herrenschmidt
2017-04-18 22:46 ` Benjamin Herrenschmidt
2017-04-18 22:52 ` Dan Williams
2017-04-18 18:30 ` Logan Gunthorpe
2017-04-18 19:01 ` Jason Gunthorpe
2017-04-18 19:35 ` Logan Gunthorpe
2017-04-18 19:48 ` Dan Williams
2017-04-18 20:29 ` Jerome Glisse
2017-04-18 20:31 ` Dan Williams
2017-04-18 20:48 ` Logan Gunthorpe
2017-04-19 1:17 ` Benjamin Herrenschmidt
2017-04-18 21:03 ` Jason Gunthorpe
2017-04-18 21:11 ` Dan Williams
2017-04-18 21:22 ` Jason Gunthorpe
2017-04-18 21:36 ` Dan Williams
2017-04-18 22:15 ` Logan Gunthorpe
2017-04-18 22:28 ` Dan Williams
2017-04-18 22:42 ` Jason Gunthorpe
2017-04-18 22:51 ` Dan Williams
2017-04-18 23:21 ` Jason Gunthorpe
2017-04-19 1:25 ` Benjamin Herrenschmidt
2017-04-18 22:48 ` Logan Gunthorpe
2017-04-18 22:50 ` Dan Williams
2017-04-18 22:56 ` Logan Gunthorpe [this message]
2017-04-18 23:02 ` Dan Williams
2017-04-19 1:21 ` Benjamin Herrenschmidt
2017-04-18 21:31 ` Logan Gunthorpe
2017-04-18 22:24 ` Jason Gunthorpe
2017-04-18 23:03 ` Logan Gunthorpe
2017-04-19 1:23 ` Benjamin Herrenschmidt
2017-04-19 1:20 ` Benjamin Herrenschmidt
2017-04-19 15:55 ` Jason Gunthorpe
2017-04-19 16:48 ` Logan Gunthorpe
2017-04-19 17:01 ` Dan Williams
2017-04-19 17:32 ` Jerome Glisse
2017-04-19 17:41 ` Dan Williams
2017-04-19 18:11 ` Logan Gunthorpe
2017-04-19 18:19 ` Logan Gunthorpe
2017-04-19 18:30 ` Dan Williams
2017-04-19 18:41 ` Logan Gunthorpe
2017-04-19 18:44 ` Dan Williams
2017-04-20 20:43 ` Stephen Bates
2017-04-20 20:47 ` Dan Williams
2017-04-20 23:07 ` Stephen Bates
2017-04-21 4:59 ` Dan Williams
2017-04-19 17:14 ` Jason Gunthorpe
2017-04-19 18:01 ` Logan Gunthorpe
2017-04-19 18:32 ` Jason Gunthorpe
2017-04-19 19:02 ` Logan Gunthorpe
2017-04-19 19:31 ` Jason Gunthorpe
2017-04-19 19:41 ` Logan Gunthorpe
2017-04-19 20:48 ` Jason Gunthorpe
2017-04-19 22:55 ` Logan Gunthorpe
2017-04-20 0:07 ` Dan Williams
2017-04-18 19:48 ` Jason Gunthorpe
2017-04-18 20:06 ` Logan Gunthorpe
-- strict thread matches above, loose matches on Subject: below --
2017-03-30 22:12 Logan Gunthorpe
2017-04-12 5:22 ` Benjamin Herrenschmidt
2017-04-12 17:09 ` Logan Gunthorpe
2017-04-12 21:55 ` Benjamin Herrenschmidt
2017-04-13 21:22 ` Logan Gunthorpe
2017-04-13 22:37 ` Benjamin Herrenschmidt
2017-04-13 23:26 ` Bjorn Helgaas
2017-04-14 4:16 ` Jason Gunthorpe
2017-04-14 4:40 ` Logan Gunthorpe
2017-04-14 11:37 ` Benjamin Herrenschmidt
2017-04-14 11:39 ` Benjamin Herrenschmidt
2017-04-14 11:37 ` Benjamin Herrenschmidt
2017-04-14 17:30 ` Logan Gunthorpe
2017-04-14 19:04 ` Bjorn Helgaas
2017-04-14 22:07 ` Benjamin Herrenschmidt
2017-04-15 17:41 ` Logan Gunthorpe
2017-04-15 22:09 ` Dan Williams
2017-04-16 3:01 ` Benjamin Herrenschmidt
2017-04-16 4:46 ` Logan Gunthorpe
2017-04-16 15:53 ` Dan Williams
2017-04-16 16:34 ` Logan Gunthorpe
2017-04-16 22:31 ` Benjamin Herrenschmidt
2017-04-24 7:36 ` Knut Omang
2017-04-24 16:14 ` Logan Gunthorpe
2017-04-25 6:30 ` Knut Omang
2017-04-25 17:03 ` Logan Gunthorpe
2017-04-25 21:23 ` Stephen Bates
2017-04-25 21:23 ` Stephen Bates
2017-04-16 22:26 ` Benjamin Herrenschmidt
2017-04-15 22:17 ` Benjamin Herrenschmidt
2017-04-16 5:36 ` Logan Gunthorpe
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