From: Bjorn Helgaas <helgaas@kernel.org>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
linux-mm@kvack.org, iommu@lists.linux-foundation.org,
"Stephen Bates" <sbates@raithlin.com>,
"Christoph Hellwig" <hch@lst.de>,
"Dan Williams" <dan.j.williams@intel.com>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Christian König" <christian.koenig@amd.com>,
"Ira Weiny" <iweiny@intel.com>,
"John Hubbard" <jhubbard@nvidia.com>,
"Don Dutile" <ddutile@redhat.com>,
"Matthew Wilcox" <willy@infradead.org>,
"Daniel Vetter" <daniel.vetter@ffwll.ch>
Subject: Re: [RFC PATCH 03/15] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset()
Date: Tue, 10 Nov 2020 17:25:13 -0600 [thread overview]
Message-ID: <20201110232513.GA705726@bjorn-Precision-5520> (raw)
In-Reply-To: <20201106170036.18713-4-logang@deltatee.com>
On Fri, Nov 06, 2020 at 10:00:24AM -0700, Logan Gunthorpe wrote:
> Introduce pci_p2pdma_should_map_bus() which is meant to be called by
> dma map functions to determine how to map a given p2pdma page.
s/dma/DMA/ for consistency (also below in function comment)
> pci_p2pdma_bus_offset() is also added to allow callers to get the bus
> offset if they need to map the bus address.
>
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> ---
> drivers/pci/p2pdma.c | 46 ++++++++++++++++++++++++++++++++++++++
> include/linux/pci-p2pdma.h | 11 +++++++++
> 2 files changed, 57 insertions(+)
>
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index ea8472278b11..9961e779f430 100644
> --- a/drivers/pci/p2pdma.c
> +++ b/drivers/pci/p2pdma.c
> @@ -930,6 +930,52 @@ void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
> }
> EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_sg_attrs);
>
> +/**
> + * pci_p2pdma_bus_offset - returns the bus offset for a given page
> + * @page: page to get the offset for
> + *
> + * Must be passed a pci p2pdma page.
s/pci/PCI/
> + */
> +u64 pci_p2pdma_bus_offset(struct page *page)
> +{
> + struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(page->pgmap);
> +
> + WARN_ON(!is_pci_p2pdma_page(page));
> +
> + return p2p_pgmap->bus_offset;
> +}
> +EXPORT_SYMBOL_GPL(pci_p2pdma_bus_offset);
> +
> +/**
> + * pci_p2pdma_should_map_bus - determine if a dma mapping should use the
> + * bus address
> + * @dev: device doing the DMA request
> + * @pgmap: dev_pagemap structure for the mapping
> + *
> + * Returns 1 if the page should be mapped with a bus address, 0 otherwise
> + * and -1 the device should not be mapping P2PDMA pages.
I think this is missing a word.
I'm not really sure how to interpret the "should" in
pci_p2pdma_should_map_bus(). If this returns -1, does that mean the
patches *cannot* be mapped? They *could* be mapped, but you really
*shouldn't*? Something else?
1 means page should be mapped with bus address. 0 means ... what,
exactly? It should be mapped with some different address?
Sorry these are naive questions because I don't know how all this
works.
> + */
> +int pci_p2pdma_should_map_bus(struct device *dev, struct dev_pagemap *pgmap)
> +{
> + struct pci_p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(pgmap);
> + struct pci_dev *client;
> +
> + if (!dev_is_pci(dev))
> + return -1;
> +
> + client = to_pci_dev(dev);
> +
> + switch (pci_p2pdma_map_type(p2p_pgmap->provider, client)) {
> + case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:
> + return 0;
> + case PCI_P2PDMA_MAP_BUS_ADDR:
> + return 1;
> + default:
> + return -1;
> + }
> +}
> +EXPORT_SYMBOL_GPL(pci_p2pdma_should_map_bus);
> +
> /**
> * pci_p2pdma_enable_store - parse a configfs/sysfs attribute store
> * to enable p2pdma
> diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h
> index 8318a97c9c61..fc5de47eeac4 100644
> --- a/include/linux/pci-p2pdma.h
> +++ b/include/linux/pci-p2pdma.h
> @@ -34,6 +34,8 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
> int nents, enum dma_data_direction dir, unsigned long attrs);
> void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
> int nents, enum dma_data_direction dir, unsigned long attrs);
> +u64 pci_p2pdma_bus_offset(struct page *page);
> +int pci_p2pdma_should_map_bus(struct device *dev, struct dev_pagemap *pgmap);
> int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,
> bool *use_p2pdma);
> ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
> @@ -83,6 +85,15 @@ 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 u64 pci_p2pdma_bus_offset(struct page *page)
> +{
> + return -1;
> +}
> +static inline int pci_p2pdma_should_map_bus(struct device *dev,
> + struct dev_pagemap *pgmap)
> +{
> + return -1;
> +}
> static inline int pci_p2pdma_map_sg_attrs(struct device *dev,
> struct scatterlist *sg, int nents, enum dma_data_direction dir,
> unsigned long attrs)
> --
> 2.20.1
>
next prev parent reply other threads:[~2020-11-10 23:25 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-06 17:00 [RFC PATCH 00/15] Userspace P2PDMA with O_DIRECT NVMe devices Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 01/15] PCI/P2PDMA: Don't sleep in upstream_bridge_distance_warn() Logan Gunthorpe
2020-11-09 9:12 ` Christoph Hellwig
2020-11-06 17:00 ` [RFC PATCH 02/15] PCI/P2PDMA: Attempt to set map_type if it has not been set Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 03/15] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset() Logan Gunthorpe
2020-11-10 23:25 ` Bjorn Helgaas [this message]
2020-11-10 23:42 ` Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 04/15] lib/scatterlist: Add flag for indicating P2PDMA segments in an SGL Logan Gunthorpe
2020-11-09 9:12 ` Christoph Hellwig
2020-11-09 14:02 ` Robin Murphy
2020-11-09 16:47 ` Logan Gunthorpe
2020-12-10 1:22 ` Dan Williams
2020-12-10 2:06 ` Logan Gunthorpe
2020-12-10 4:04 ` Dan Williams
2020-12-10 16:44 ` Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 05/15] dma-direct: Support PCI P2PDMA pages in dma-direct map_sg Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 06/15] dma-mapping: Add flags to dma_map_ops to indicate PCI P2PDMA support Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 07/15] iommu/dma: Support PCI P2PDMA pages in dma-iommu map_sg Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 08/15] nvme-pci: Check DMA ops when indicating support for PCI P2PDMA Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 09/15] nvme-pci: Convert to using dma_map_sg for p2pdma pages Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 10/15] mm: Introduce FOLL_PCI_P2PDMA to gate getting PCI P2PDMA pages Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 11/15] iov_iter: Introduce iov_iter_get_pages_[alloc_]flags() Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 12/15] block: Set FOLL_PCI_P2PDMA in __bio_iov_iter_get_pages() Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 13/15] block: Set FOLL_PCI_P2PDMA in bio_map_user_iov() Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 14/15] PCI/P2PDMA: Introduce pci_mmap_p2pmem() Logan Gunthorpe
2020-11-06 17:22 ` Jason Gunthorpe
2020-11-06 17:28 ` Logan Gunthorpe
2020-11-06 17:42 ` Jason Gunthorpe
2020-11-06 17:53 ` Logan Gunthorpe
2020-11-06 18:09 ` Jason Gunthorpe
2020-11-06 18:20 ` Logan Gunthorpe
2020-11-06 19:30 ` Jason Gunthorpe
2020-11-06 19:44 ` Logan Gunthorpe
2020-11-06 19:53 ` Jason Gunthorpe
2020-11-06 20:03 ` Logan Gunthorpe
2020-11-07 0:14 ` Jason Gunthorpe
2020-11-07 2:50 ` Logan Gunthorpe
2020-11-06 17:00 ` [RFC PATCH 15/15] nvme-pci: Allow mmaping the CMB in userspace Logan Gunthorpe
2020-11-06 17:39 ` Jason Gunthorpe
2020-11-06 17:43 ` Logan Gunthorpe
2020-11-09 15:03 ` Keith Busch
2020-11-09 16:50 ` Logan Gunthorpe
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