From: Jason Gunthorpe <jgg@mellanox.com>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: "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>,
Bjorn Helgaas <bhelgaas@google.com>,
Christoph Hellwig <hch@lst.de>,
Christian Koenig <Christian.Koenig@amd.com>,
Sagi Grimberg <sagi@grimberg.me>, Keith Busch <kbusch@kernel.org>,
Jens Axboe <axboe@fb.com>,
Dan Williams <dan.j.williams@intel.com>,
Eric Pilmore <epilmore@gigaio.com>,
Stephen Bates <sbates@raithlin.com>
Subject: Re: [PATCH 11/14] PCI/P2PDMA: dma_map P2PDMA map requests that traverse the host bridge
Date: Thu, 25 Jul 2019 19:29:49 +0000 [thread overview]
Message-ID: <20190725192944.GI7450@mellanox.com> (raw)
In-Reply-To: <cf61d237-8a8a-e3ac-a9df-466f20b63020@deltatee.com>
On Thu, Jul 25, 2019 at 01:17:02PM -0600, Logan Gunthorpe wrote:
>
>
> On 2019-07-25 12:58 p.m., Jason Gunthorpe wrote:
> > On Mon, Jul 22, 2019 at 05:08:56PM -0600, Logan Gunthorpe wrote:
> >> Any requests that traverse the host bridge will need to be mapped into
> >> the IOMMU, so call dma_map_sg() inside pci_p2pdma_map_sg() when
> >> appropriate.
> >>
> >> Similarly, call dma_unmap_sg() inside pci_p2pdma_unmap_sg().
> >>
> >> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> >> drivers/pci/p2pdma.c | 31 ++++++++++++++++++++++++++++++-
> >> 1 file changed, 30 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> >> index 5f43f92f9336..76f51678342c 100644
> >> +++ b/drivers/pci/p2pdma.c
> >> @@ -830,8 +830,22 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
> >> int nents, enum dma_data_direction dir, unsigned long attrs)
> >> {
> >> struct dev_pagemap *pgmap = sg_page(sg)->pgmap;
> >> + struct pci_dev *client;
> >> + int dist;
> >> +
> >> + client = find_parent_pci_dev(dev);
> >> + if (WARN_ON_ONCE(!client))
> >> + return 0;
> >>
> >> - return __pci_p2pdma_map_sg(pgmap, dev, sg, nents);
> >> + dist = upstream_bridge_distance(pgmap->pci_p2pdma_provider,
> >> + client, NULL);
Isn't is a bit of a leap to assume that the pgmap is uniform across
all the sgs?
> >> + if (WARN_ON_ONCE(dist & P2PDMA_NOT_SUPPORTED))
> >> + return 0;
> >> +
> >> + if (dist & P2PDMA_THRU_HOST_BRIDGE)
> >> + return dma_map_sg_attrs(dev, sg, nents, dir, attrs);
> >
> > IIRC at this point the SG will have struct page references to the BAR
> > memory - so (all?) the IOMMU drivers are able to handle P2P setup in
> > this case?
>
> Yes. The IOMMU drivers refer to the physical address for BAR which they
> can get from the struct page. And this works fine today.
Interesting.
So, for the places where we already map BAR memory to userspace, if I
were to make struct pages for those BARs and use vm_insert_page()
instead of io_remap_pfn_range(), then the main thing missing in RDMA
to actually do P2P DMA is a way to get those struct pages out of
get_user_pages and know to call the pci_p2pdma_map_sg version (ie in
ib_umem_get())?
Jason
next prev parent reply other threads:[~2019-07-25 19:30 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-22 23:08 [PATCH 00/14] PCI/P2PDMA: Support transactions that hit the host bridge Logan Gunthorpe
2019-07-22 23:08 ` [PATCH 01/14] PCI/P2PDMA: Add constants for not-supported result upstream_bridge_distance() Logan Gunthorpe
2019-07-23 16:20 ` Koenig, Christian
2019-07-22 23:08 ` [PATCH 02/14] PCI/P2PDMA: Factor out __upstream_bridge_distance() Logan Gunthorpe
2019-07-22 23:08 ` [PATCH 03/14] PCI/P2PDMA: Apply host bridge white list for ACS Logan Gunthorpe
2019-07-23 16:23 ` Koenig, Christian
2019-07-22 23:08 ` [PATCH 04/14] PCI/P2PDMA: Cache the result of upstream_bridge_distance() Logan Gunthorpe
2019-07-22 23:08 ` [PATCH 05/14] PCI/P2PDMA: Factor out host_bridge_whitelist() Logan Gunthorpe
2019-07-22 23:08 ` [PATCH 06/14] PCI/P2PDMA: Add whitelist support for Intel Host Bridges Logan Gunthorpe
2019-07-25 18:52 ` Jason Gunthorpe
2019-07-25 19:14 ` Logan Gunthorpe
2019-07-22 23:08 ` [PATCH 07/14] PCI/P2PDMA: Add the provider's pci_dev to the dev_pgmap struct Logan Gunthorpe
2019-07-24 6:32 ` Christoph Hellwig
2019-07-24 15:50 ` Logan Gunthorpe
2019-07-25 6:02 ` Christoph Hellwig
2019-07-22 23:08 ` [PATCH 08/14] PCI/P2PDMA: Add attrs argument to pci_p2pdma_map_sg() Logan Gunthorpe
2019-07-22 23:08 ` [PATCH 09/14] PCI/P2PDMA: Introduce pci_p2pdma_unmap_sg() Logan Gunthorpe
2019-07-22 23:08 ` [PATCH 10/14] PCI/P2PDMA: Factor out __pci_p2pdma_map_sg() Logan Gunthorpe
2019-07-22 23:08 ` [PATCH 11/14] PCI/P2PDMA: dma_map P2PDMA map requests that traverse the host bridge Logan Gunthorpe
2019-07-24 6:32 ` Christoph Hellwig
2019-07-24 15:58 ` Logan Gunthorpe
2019-07-25 6:10 ` Christoph Hellwig
2019-07-25 16:00 ` Logan Gunthorpe
2019-07-25 16:34 ` Jason Gunthorpe
2019-07-25 17:22 ` Logan Gunthorpe
2019-07-25 18:58 ` Jason Gunthorpe
2019-07-25 19:17 ` Logan Gunthorpe
2019-07-25 19:29 ` Jason Gunthorpe [this message]
2019-07-25 19:36 ` Logan Gunthorpe
2019-07-22 23:08 ` [PATCH 12/14] PCI/P2PDMA: No longer require no-mmu for host bridge whitelist Logan Gunthorpe
2019-07-22 23:08 ` [PATCH 13/14] PCI/P2PDMA: Update documentation for pci_p2pdma_distance_many() Logan Gunthorpe
2019-07-22 23:08 ` [PATCH 14/14] PCI/P2PDMA: Introduce pci_p2pdma_[un]map_resource() Logan Gunthorpe
2019-07-23 16:28 ` Koenig, Christian
2019-07-23 16:58 ` Logan Gunthorpe
2019-07-24 6:32 ` Christoph Hellwig
2019-07-24 16:06 ` Logan Gunthorpe
2019-07-25 11:50 ` Christoph Hellwig
2019-07-25 16:00 ` Logan Gunthorpe
2019-07-23 16:30 ` [PATCH 00/14] PCI/P2PDMA: Support transactions that hit the host bridge Koenig, Christian
2019-07-23 16:58 ` Logan Gunthorpe
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