linux-kernel - [RFC PATCH 03/15] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus

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Message-Id: <20201106170036.18713-4-logang@deltatee.com>
Date:   Fri,  6 Nov 2020 10:00:24 -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>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [RFC PATCH 03/15] 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       | 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.
+ */
+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.
+ */
+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