Messages in this thread | | | From | Logan Gunthorpe <> | Date | Thu, 25 Jul 2019 13:17:02 -0600 | Subject | Re: [PATCH 11/14] PCI/P2PDMA: dma_map P2PDMA map requests that traverse the host bridge |
| |
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); >> + 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.
> Didn't you also have a patch to remove the struct page's for the BAR > memory?
Well that was an RFC that's not going anywhere in it's current form. I'd still like to remove struct pages but that's going to take a while and when that happens, this will have to be reworked. Probably to use dma_map_resource() instead but will depend on the form the removal takes.
Logan
| |