linux-kernel - [RFC PATCH v2 04/11] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus

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Date:   Thu, 11 Mar 2021 16:31:34 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org
Cc:     Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christian König <christian.koenig@....com>,
        Ira Weiny <iweiny@...el.com>,
        John Hubbard <jhubbard@...dia.com>,
        Don Dutile <ddutile@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Jakowski Andrzej <andrzej.jakowski@...el.com>,
        Minturn Dave B <dave.b.minturn@...el.com>,
        Jason Ekstrand <jason@...kstrand.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Xiong Jianxin <jianxin.xiong@...el.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [RFC PATCH v2 04/11] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset()

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.

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@...tatee.com>
---
 drivers/pci/p2pdma.c       | 50 ++++++++++++++++++++++++++++++++++++++
 include/linux/pci-p2pdma.h | 11 +++++++++
 2 files changed, 61 insertions(+)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 7f6836732bce..66d16b7eb668 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -912,6 +912,56 @@ 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.
+ */
+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_dma_map_type - determine if a DMA mapping should use the
+ *	bus address, be mapped normally or fail
+ * @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 - if the page should be mapped normally through an IOMMU mapping or
+ *        physical address; or
+ *   -1 - if the device should not map the pages and an error should be
+ *        returned
+ */
+int pci_p2pdma_dma_map_type(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_dma_map_type);
+
 /**
  * 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..3d55ad19f54c 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_dma_map_type(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_dma_map_type(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