From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 6D197211518CA for ; Fri, 21 Sep 2018 06:15:52 -0700 (PDT) Date: Fri, 21 Sep 2018 08:15:50 -0500 From: Bjorn Helgaas Subject: Re: [PATCH v6 03/13] PCI/P2PDMA: Add PCI p2pmem DMA mappings to adjust the bus offset Message-ID: <20180921131550.GG224714@bhelgaas-glaptop.roam.corp.google.com> References: <20180913001156.4115-1-logang@deltatee.com> <20180913001156.4115-4-logang@deltatee.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20180913001156.4115-4-logang@deltatee.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Logan Gunthorpe Cc: Jens Axboe , Alex Williamson , linux-nvdimm@lists.01.org, linux-rdma@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, =?iso-8859-1?B?Suly9G1l?= Glisse , Jason Gunthorpe , Christian =?iso-8859-1?Q?K=F6nig?= , Benjamin Herrenschmidt , Bjorn Helgaas , Max Gurtovoy , Christoph Hellwig List-ID: On Wed, Sep 12, 2018 at 06:11:46PM -0600, Logan Gunthorpe wrote: > The DMA address used when mapping PCI P2P memory must be the PCI bus > address. Thus, introduce pci_p2pmem_map_sg() to map the correct > addresses when using P2P memory. Memory mapped in this way does not > need to be unmapped. I think the use of "map" in this context is slightly confusing because the general expectation is that map/unmap must be balanced. I assume it's because the "mapping" consumes no resources, e.g., requires no page table entries. Possibly there's a better verb than "map", e.g., "convert", "convert_to_p2pdma", etc? If you keep "map", maybe add a sentence or two about why there's no corresponding unmap? > For this, we assume that an SGL passed to these functions contain all > P2P memory or no P2P memory. > > Signed-off-by: Logan Gunthorpe Acked-by: Bjorn Helgaas > --- > drivers/pci/p2pdma.c | 43 ++++++++++++++++++++++++++++++++++++++ > include/linux/memremap.h | 1 + > include/linux/pci-p2pdma.h | 7 +++++++ > 3 files changed, 51 insertions(+) > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > index 67c1daf1189e..29bd40a87768 100644 > --- a/drivers/pci/p2pdma.c > +++ b/drivers/pci/p2pdma.c > @@ -191,6 +191,8 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size, > pgmap->res.flags = pci_resource_flags(pdev, bar); > pgmap->ref = &pdev->p2pdma->devmap_ref; > pgmap->type = MEMORY_DEVICE_PCI_P2PDMA; > + pgmap->pci_p2pdma_bus_offset = pci_bus_address(pdev, bar) - > + pci_resource_start(pdev, bar); > > addr = devm_memremap_pages(&pdev->dev, pgmap); > if (IS_ERR(addr)) { > @@ -813,3 +815,44 @@ void pci_p2pmem_publish(struct pci_dev *pdev, bool publish) > pdev->p2pdma->p2pmem_published = publish; > } > EXPORT_SYMBOL_GPL(pci_p2pmem_publish); > + > +/** > + * pci_p2pdma_map_sg - map a PCI peer-to-peer scatterlist for DMA > + * @dev: device doing the DMA request > + * @sg: scatter list to map > + * @nents: elements in the scatterlist > + * @dir: DMA direction > + * > + * Scatterlists mapped with this function should not be unmapped in any way. > + * > + * Returns the number of SG entries mapped or 0 on error. > + */ > +int pci_p2pdma_map_sg(struct device *dev, struct scatterlist *sg, int nents, > + enum dma_data_direction dir) > +{ > + struct dev_pagemap *pgmap; > + struct scatterlist *s; > + phys_addr_t paddr; > + int i; > + > + /* > + * p2pdma mappings are not compatible with devices that use > + * dma_virt_ops. If the upper layers do the right thing > + * this should never happen because it will be prevented > + * by the check in pci_p2pdma_add_client() > + */ > + if (WARN_ON_ONCE(IS_ENABLED(CONFIG_DMA_VIRT_OPS) && > + dev->dma_ops == &dma_virt_ops)) > + return 0; > + > + for_each_sg(sg, s, nents, i) { > + pgmap = sg_page(s)->pgmap; > + paddr = sg_phys(s); > + > + s->dma_address = paddr - pgmap->pci_p2pdma_bus_offset; > + sg_dma_len(s) = s->length; > + } > + > + return nents; > +} > +EXPORT_SYMBOL_GPL(pci_p2pdma_map_sg); > diff --git a/include/linux/memremap.h b/include/linux/memremap.h > index 9553370ebdad..0ac69ddf5fc4 100644 > --- a/include/linux/memremap.h > +++ b/include/linux/memremap.h > @@ -125,6 +125,7 @@ struct dev_pagemap { > struct device *dev; > void *data; > enum memory_type type; > + u64 pci_p2pdma_bus_offset; > }; > > #ifdef CONFIG_ZONE_DEVICE > diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h > index 7b2b0f547528..2f03dbbf5af6 100644 > --- a/include/linux/pci-p2pdma.h > +++ b/include/linux/pci-p2pdma.h > @@ -36,6 +36,8 @@ struct scatterlist *pci_p2pmem_alloc_sgl(struct pci_dev *pdev, > unsigned int *nents, u32 length); > void pci_p2pmem_free_sgl(struct pci_dev *pdev, struct scatterlist *sgl); > void pci_p2pmem_publish(struct pci_dev *pdev, bool publish); > +int pci_p2pdma_map_sg(struct device *dev, struct scatterlist *sg, int nents, > + enum dma_data_direction dir); > #else /* CONFIG_PCI_P2PDMA */ > static inline int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, > size_t size, u64 offset) > @@ -98,5 +100,10 @@ static inline void pci_p2pmem_free_sgl(struct pci_dev *pdev, > static inline void pci_p2pmem_publish(struct pci_dev *pdev, bool publish) > { > } > +static inline int pci_p2pdma_map_sg(struct device *dev, > + struct scatterlist *sg, int nents, enum dma_data_direction dir) > +{ > + return 0; > +} > #endif /* CONFIG_PCI_P2PDMA */ > #endif /* _LINUX_PCI_P2P_H */ > -- > 2.19.0 > _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm