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From: Alex Williamson <alex.williamson@redhat.com>
To: Don Dutile <ddutile@redhat.com>
Cc: "Stephen Bates" <sbates@raithlin.com>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Logan Gunthorpe" <logang@deltatee.com>,
	"Linux Kernel Mailing List" <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 <linux-rdma@vger.kernel.org>,
	linux-nvdimm <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>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
	"Christian König" <christian.koenig@amd.com>
Subject: Re: [PATCH v4 04/14] PCI/P2PDMA: Clear ACS P2P flags for all devices behind switches
Date: Tue, 8 May 2018 18:01:57 -0600	[thread overview]
Message-ID: <20180508180157.7c7b393f@w520.home> (raw)
In-Reply-To: <c5f30ced-7bbf-9420-db1a-72519fc78b3a@redhat.com>

On Tue, 8 May 2018 19:06:17 -0400
Don Dutile <ddutile@redhat.com> wrote:
> On 05/08/2018 05:27 PM, Stephen  Bates wrote:
> > As I understand it VMs need to know because VFIO passes IOMMU
> > grouping up into the VMs. So if a IOMMU grouping changes the VM's
> > view of its PCIe topology changes. I think we even have to be
> > cognizant of the fact the OS running on the VM may not even support
> > hot-plug of PCI devices.  
> Alex:
> Really? IOMMU groups are created by the kernel, so don't know how
> they would be passed into the VMs, unless indirectly via  PCI(e)
> layout. At best, twiddling w/ACS enablement (emulation) would cause
> VMs to see different IOMMU groups, but again, VMs are not the
> security point/level, the host/HV's are.

Correct, the VM has no concept of the host's IOMMU groups, only the
hypervisor knows about the groups, but really only to the extent of
which device belongs to which group and whether the group is viable.
Any runtime change to grouping though would require DMA mapping
updates, which I don't see how we can reasonably do with drivers,
vfio-pci or native host drivers, bound to the affected devices.  Thanks,

Alex

  reply	other threads:[~2018-05-09  0:02 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
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 [this message]
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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