PCI/P2PDMA: Refactor the p2pdma mapping helpers

The current scheme with a single helper to determine the P2P status
and map a scatterlist segment force users to always use the map_sg
helper to DMA map, which we're trying to get away from because they
are very cache inefficient.

Refactor the code so that there is a single helper that checks the P2P
state for a page, including the result that it is not a P2P page to
simplify the callers, and a second one to perform the address translation
for a bus mapped P2P transfer that does not depend on the scatterlist
structure.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

1 files changed, 41 insertions, 10 deletions

diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index e172522cd936..c3086edeccc6 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -444,6 +444,11 @@ enum pci_p2pdma_map_type {
 	PCI_P2PDMA_MAP_UNKNOWN = 0,
 
 	/*
+	 * Not a PCI P2PDMA transfer.
+	 */
+	PCI_P2PDMA_MAP_NONE,
+
+	/*
 	 * PCI_P2PDMA_MAP_NOT_SUPPORTED: Indicates the transaction will
 	 * traverse the host bridge and the host bridge is not in the
 	 * allowlist. DMA Mapping routines should return an error when
@@ -471,21 +476,47 @@ enum pci_p2pdma_map_type {
 
 struct pci_p2pdma_map_state {
 	struct dev_pagemap *pgmap;
-	int map;
+	enum pci_p2pdma_map_type map;
 	u64 bus_off;
 };
 
-#ifdef CONFIG_PCI_P2PDMA
-enum pci_p2pdma_map_type
-pci_p2pdma_map_segment(struct pci_p2pdma_map_state *state, struct device *dev,
-		       struct scatterlist *sg);
-#else /* CONFIG_PCI_P2PDMA */
+/* helper for pci_p2pdma_state(), do not use directly */
+void __pci_p2pdma_update_state(struct pci_p2pdma_map_state *state,
+		struct device *dev, struct page *page);
+
+/**
+ * pci_p2pdma_state - check the P2P transfer state of a page
+ * @state:	P2P state structure
+ * @dev:	device to transfer to/from
+ * @page:	page to map
+ *
+ * Check if @page is a PCI P2PDMA page, and if yes of what kind.  Returns the
+ * map type, and updates @state with all information needed for a P2P transfer.
+ */
 static inline enum pci_p2pdma_map_type
-pci_p2pdma_map_segment(struct pci_p2pdma_map_state *state, struct device *dev,
-		       struct scatterlist *sg)
+pci_p2pdma_state(struct pci_p2pdma_map_state *state, struct device *dev,
+		struct page *page)
+{
+	if (IS_ENABLED(CONFIG_PCI_P2PDMA) && is_pci_p2pdma_page(page)) {
+		if (state->pgmap != page_pgmap(page))
+			__pci_p2pdma_update_state(state, dev, page);
+		return state->map;
+	}
+	return PCI_P2PDMA_MAP_NONE;
+}
+
+/**
+ * pci_p2pdma_bus_addr_map - map a PCI_P2PDMA_MAP_BUS_ADDR P2P transfer
+ * @state:	P2P state structure
+ * @paddr:	physical address to map
+ *
+ * Map a physically contiguous PCI_P2PDMA_MAP_BUS_ADDR transfer.
+ */
+static inline dma_addr_t
+pci_p2pdma_bus_addr_map(struct pci_p2pdma_map_state *state, phys_addr_t paddr)
 {
-	return PCI_P2PDMA_MAP_NOT_SUPPORTED;
+	WARN_ON_ONCE(state->map != PCI_P2PDMA_MAP_BUS_ADDR);
+	return paddr + state->bus_off;
 }
-#endif /* CONFIG_PCI_P2PDMA */
 
 #endif /* _LINUX_DMA_MAP_OPS_H */