From: Alex Williamson <alex.williamson@redhat.com>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: "Stephen Bates" <sbates@raithlin.com>,
"Christian König" <christian.koenig@amd.com>,
"Bjorn Helgaas" <helgaas@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"Christoph Hellwig" <hch@lst.de>, "Jens Axboe" <axboe@kernel.dk>,
"Keith Busch" <keith.busch@intel.com>,
"Sagi Grimberg" <sagi@grimberg.me>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Jason Gunthorpe" <jgg@mellanox.com>,
"Max Gurtovoy" <maxg@mellanox.com>,
"Dan Williams" <dan.j.williams@intel.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Benjamin Herrenschmidt" <benh@kernel.crashing.org>
Subject: Re: [PATCH v4 04/14] PCI/P2PDMA: Clear ACS P2P flags for all devices behind switches
Date: Tue, 8 May 2018 16:32:06 -0600 [thread overview]
Message-ID: <20180508163206.7d3bf383@w520.home> (raw)
In-Reply-To: <20905682-9440-7d4b-0260-99d3dc794c3d@deltatee.com>
On Tue, 8 May 2018 16:10:19 -0600
Logan Gunthorpe <logang@deltatee.com> wrote:
> On 08/05/18 04:03 PM, Alex Williamson wrote:
> > If IOMMU grouping implies device assignment (because nobody else uses
> > it to the same extent as device assignment) then the build-time option
> > falls to pieces, we need a single kernel that can do both. I think we
> > need to get more clever about allowing the user to specify exactly at
> > which points in the topology they want to disable isolation. Thanks,
>
>
> Yeah, so based on the discussion I'm leaning toward just having a
> command line option that takes a list of BDFs and disables ACS for them.
> (Essentially as Dan has suggested.) This avoids the shotgun.
>
> Then, the pci_p2pdma_distance command needs to check that ACS is
> disabled for all bridges between the two devices. If this is not the
> case, it returns -1. Future work can check if the EP has ATS support, in
> which case it has to check for the ACS direct translated bit.
>
> A user then needs to either disable the IOMMU and/or add the command
> line option to disable ACS for the specific downstream ports in the PCI
> hierarchy. This means the IOMMU groups will be less granular but
> presumably the person adding the command line argument understands this.
>
> We may also want to do some work so that there's informative dmesgs on
> which BDFs need to be specified on the command line so it's not so
> difficult for the user to figure out.
I'd advise caution with a user supplied BDF approach, we have no
guaranteed persistence for a device's PCI address. Adding a device
might renumber the buses, replacing a device with one that consumes
more/less bus numbers can renumber the buses, motherboard firmware
updates could renumber the buses, pci=assign-buses can renumber the
buses, etc. This is why the VT-d spec makes use of device paths when
describing PCI hierarchies, firmware can't know what bus number will be
assigned to a device, but it does know the base bus number and the path
of devfns needed to get to it. I don't know how we come up with an
option that's easy enough for a user to understand, but reasonably
robust against hardware changes. Thanks,
Alex
next prev parent reply other threads:[~2018-05-08 22:32 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-23 23:30 [PATCH v4 00/14] Copy Offload in NVMe Fabrics with P2P PCI Memory Logan Gunthorpe
2018-04-23 23:30 ` [PATCH v4 01/14] PCI/P2PDMA: Support peer-to-peer memory Logan Gunthorpe
2018-05-07 23:00 ` Bjorn Helgaas
2018-05-07 23:09 ` Logan Gunthorpe
2018-04-23 23:30 ` [PATCH v4 02/14] PCI/P2PDMA: Add sysfs group to display p2pmem stats Logan Gunthorpe
2018-04-23 23:30 ` [PATCH v4 03/14] PCI/P2PDMA: Add PCI p2pmem dma mappings to adjust the bus offset Logan Gunthorpe
2018-05-07 23:02 ` Bjorn Helgaas
2018-04-23 23:30 ` [PATCH v4 04/14] PCI/P2PDMA: Clear ACS P2P flags for all devices behind switches Logan Gunthorpe
2018-04-24 3:33 ` Randy Dunlap
2018-05-07 23:13 ` Bjorn Helgaas
2018-05-08 7:17 ` Christian König
2018-05-08 14:25 ` Stephen Bates
2018-05-08 16:37 ` Christian König
2018-05-08 16:27 ` Logan Gunthorpe
2018-05-08 16:50 ` Christian König
2018-05-08 19:13 ` Logan Gunthorpe
2018-05-08 19:34 ` Alex Williamson
2018-05-08 19:45 ` Logan Gunthorpe
2018-05-08 20:13 ` Alex Williamson
2018-05-08 20:19 ` Logan Gunthorpe
2018-05-08 20:43 ` Alex Williamson
2018-05-08 20:49 ` Logan Gunthorpe
2018-05-08 21:26 ` Alex Williamson
2018-05-08 21:42 ` Stephen Bates
2018-05-08 22:03 ` Alex Williamson
2018-05-08 22:10 ` Logan Gunthorpe
2018-05-08 22:25 ` Stephen Bates
2018-05-08 23:11 ` Alex Williamson
2018-05-08 23:31 ` Logan Gunthorpe
2018-05-09 0:17 ` Alex Williamson
2018-05-08 22:32 ` Alex Williamson [this message]
2018-05-08 23:00 ` Dan Williams
2018-05-08 23:15 ` Logan Gunthorpe
2018-05-09 12:38 ` Stephen Bates
2018-05-08 22:21 ` Don Dutile
2018-05-09 12:44 ` Stephen Bates
2018-05-09 15:58 ` Don Dutile
2018-05-08 20:50 ` Jerome Glisse
2018-05-08 21:35 ` Stephen Bates
2018-05-09 13:12 ` Stephen Bates
2018-05-09 13:40 ` Christian König
2018-05-09 15:41 ` Stephen Bates
2018-05-09 16:07 ` Jerome Glisse
2018-05-09 16:30 ` Stephen Bates
2018-05-09 17:49 ` Jerome Glisse
2018-05-10 14:20 ` Stephen Bates
2018-05-10 14:29 ` Christian König
2018-05-10 14:59 ` Jerome Glisse
2018-05-10 18:44 ` Stephen Bates
2018-05-09 16:45 ` Logan Gunthorpe
2018-05-10 12:52 ` Christian König
2018-05-10 14:16 ` Stephen Bates
2018-05-10 14:41 ` Jerome Glisse
2018-05-10 18:41 ` Stephen Bates
2018-05-10 18:59 ` Logan Gunthorpe
2018-05-10 19:10 ` Alex Williamson
2018-05-10 19:24 ` Jerome Glisse
2018-05-10 16:32 ` Logan Gunthorpe
2018-05-10 17:11 ` Stephen Bates
2018-05-10 17:15 ` Logan Gunthorpe
2018-05-11 8:52 ` Christian König
2018-05-11 15:48 ` Logan Gunthorpe
2018-05-11 21:50 ` Stephen Bates
2018-05-11 22:24 ` Stephen Bates
2018-05-11 22:55 ` Logan Gunthorpe
2018-05-08 14:31 ` Dan Williams
2018-05-08 14:44 ` Stephen Bates
2018-05-08 21:04 ` Don Dutile
2018-05-08 21:27 ` Stephen Bates
2018-05-08 23:06 ` Don Dutile
2018-05-09 0:01 ` Alex Williamson
2018-05-09 12:35 ` Stephen Bates
2018-05-09 14:44 ` Alex Williamson
2018-05-09 15:52 ` Don Dutile
2018-05-09 15:47 ` Don Dutile
2018-05-09 15:53 ` Don Dutile
2018-04-23 23:30 ` [PATCH v4 05/14] docs-rst: Add a new directory for PCI documentation Logan Gunthorpe
2018-04-23 23:30 ` [PATCH v4 06/14] PCI/P2PDMA: Add P2P DMA driver writer's documentation Logan Gunthorpe
2018-05-07 23:20 ` Bjorn Helgaas
2018-05-22 21:24 ` Randy Dunlap
2018-05-22 21:28 ` Logan Gunthorpe
2018-04-23 23:30 ` [PATCH v4 07/14] block: Introduce PCI P2P flags for request and request queue Logan Gunthorpe
2018-04-23 23:30 ` [PATCH v4 08/14] IB/core: Ensure we map P2P memory correctly in rdma_rw_ctx_[init|destroy]() Logan Gunthorpe
2018-04-23 23:30 ` [PATCH v4 09/14] nvme-pci: Use PCI p2pmem subsystem to manage the CMB Logan Gunthorpe
2018-04-23 23:30 ` [PATCH v4 10/14] nvme-pci: Add support for P2P memory in requests Logan Gunthorpe
2018-04-23 23:30 ` [PATCH v4 11/14] nvme-pci: Add a quirk for a pseudo CMB Logan Gunthorpe
2018-04-23 23:30 ` [PATCH v4 12/14] nvmet: Introduce helper functions to allocate and free request SGLs Logan Gunthorpe
2018-04-23 23:30 ` [PATCH v4 13/14] nvmet-rdma: Use new SGL alloc/free helper for requests Logan Gunthorpe
2018-04-23 23:30 ` [PATCH v4 14/14] nvmet: Optionally use PCI P2P memory Logan Gunthorpe
2018-05-02 11:51 ` [PATCH v4 00/14] Copy Offload in NVMe Fabrics with P2P PCI Memory Christian König
2018-05-02 15:56 ` Logan Gunthorpe
2018-05-03 9:05 ` Christian König
2018-05-03 15:59 ` Logan Gunthorpe
2018-05-03 17:29 ` Christian König
2018-05-03 18:43 ` Logan Gunthorpe
2018-05-04 14:27 ` Christian König
2018-05-04 15:52 ` Logan Gunthorpe
2018-05-07 23:23 ` Bjorn Helgaas
2018-05-07 23:34 ` Logan Gunthorpe
2018-05-08 16:57 ` Alex Williamson
2018-05-08 19:14 ` Logan Gunthorpe
2018-05-08 21:25 ` Don Dutile
2018-05-08 21:40 ` Alex Williamson
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