dma-mapping: move the PCI P2PDMA mapping helpers to pci-p2pdma.h

JIRA: https://issues.redhat.com/browse/RHEL-113839
Upstream-Status: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Conflicts: 82ba975 ("mm: allow compound zone device pages") has not been backported

commit ca2c2e4
Author: Christoph Hellwig <hch@lst.de>
Date:   Mon May 5 10:01:39 2025 +0300

    dma-mapping: move the PCI P2PDMA mapping helpers to pci-p2pdma.h

    To support the upcoming non-scatterlist mapping helpers, we need to go
    back to have them called outside of the DMA API.  Thus move them out of
    dma-map-ops.h, which is only for DMA API implementations to pci-p2pdma.h,
    which is for driver use.

    Note that the core helper is still not exported as the mapping is
    expected to be done only by very highlevel subsystem code at least for
    now.

    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>

(cherry picked from commit ca2c2e4)
Co-developed-by: Claude claude-sonnet-4
Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>

Author: snits

drivers/iommu/dma-iommu.c

@@ -26,6 +26,7 @@
 #include <linux/mutex.h>
 #include <linux/of_iommu.h>
 #include <linux/pci.h>
+#include <linux/pci-p2pdma.h>
 #include <linux/scatterlist.h>
 #include <linux/spinlock.h>
 #include <linux/swiotlb.h>

include/linux/dma-map-ops.h

@@ -434,89 +434,4 @@ static inline void debug_dma_dump_mappings(struct device *dev)
 #endif /* CONFIG_DMA_API_DEBUG */
 
 extern const struct dma_map_ops dma_dummy_ops;
-
-enum pci_p2pdma_map_type {
-	/*
-	 * PCI_P2PDMA_MAP_UNKNOWN: Used internally for indicating the mapping
-	 * type hasn't been calculated yet. Functions that return this enum
-	 * never return this value.
-	 */
-	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
-	 * this is returned.
-	 */
-	PCI_P2PDMA_MAP_NOT_SUPPORTED,
-
-	/*
-	 * PCI_P2PDMA_BUS_ADDR: Indicates that two devices can talk to
-	 * each other directly through a PCI switch and the transaction will
-	 * not traverse the host bridge. Such a mapping should program
-	 * the DMA engine with PCI bus addresses.
-	 */
-	PCI_P2PDMA_MAP_BUS_ADDR,
-
-	/*
-	 * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE: Indicates two devices can talk
-	 * to each other, but the transaction traverses a host bridge on the
-	 * allowlist. In this case, a normal mapping either with CPU physical
-	 * addresses (in the case of dma-direct) or IOVA addresses (in the
-	 * case of IOMMUs) should be used to program the DMA engine.
-	 */
-	PCI_P2PDMA_MAP_THRU_HOST_BRIDGE,
-};
-
-struct pci_p2pdma_map_state {
-	struct dev_pagemap *pgmap;
-	enum pci_p2pdma_map_type map;
-	u64 bus_off;
-};
-
-/* 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_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)
-			__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)
-{
-	WARN_ON_ONCE(state->map != PCI_P2PDMA_MAP_BUS_ADDR);
-	return paddr + state->bus_off;
-}
-
 #endif /* _LINUX_DMA_MAP_OPS_H */

include/linux/pci-p2pdma.h

@@ -104,4 +104,89 @@ static inline struct pci_dev *pci_p2pmem_find(struct device *client)
 	return pci_p2pmem_find_many(&client, 1);
 }
 
+enum pci_p2pdma_map_type {
+	/*
+	 * PCI_P2PDMA_MAP_UNKNOWN: Used internally as an initial state before
+	 * the mapping type has been calculated. Exported routines for the API
+	 * will never return this value.
+	 */
+	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
+	 * this is returned.
+	 */
+	PCI_P2PDMA_MAP_NOT_SUPPORTED,
+
+	/*
+	 * PCI_P2PDMA_MAP_BUS_ADDR: Indicates that two devices can talk to
+	 * each other directly through a PCI switch and the transaction will
+	 * not traverse the host bridge. Such a mapping should program
+	 * the DMA engine with PCI bus addresses.
+	 */
+	PCI_P2PDMA_MAP_BUS_ADDR,
+
+	/*
+	 * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE: Indicates two devices can talk
+	 * to each other, but the transaction traverses a host bridge on the
+	 * allowlist. In this case, a normal mapping either with CPU physical
+	 * addresses (in the case of dma-direct) or IOVA addresses (in the
+	 * case of IOMMUs) should be used to program the DMA engine.
+	 */
+	PCI_P2PDMA_MAP_THRU_HOST_BRIDGE,
+};
+
+struct pci_p2pdma_map_state {
+	struct dev_pagemap *pgmap;
+	enum pci_p2pdma_map_type map;
+	u64 bus_off;
+};
+
+/* 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_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)
+			__pci_p2pdma_update_state(state, dev, page);
+		return state->map;
+	}
+	return PCI_P2PDMA_MAP_NONE;
+}
+
+/**
+ * pci_p2pdma_bus_addr_map - Translate a physical address to a bus address
+ *			     for a PCI_P2PDMA_MAP_BUS_ADDR 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)
+{
+	WARN_ON_ONCE(state->map != PCI_P2PDMA_MAP_BUS_ADDR);
+	return paddr + state->bus_off;
+}
+
 #endif /* _LINUX_PCI_P2P_H */

kernel/dma/direct.c

@@ -13,6 +13,7 @@
 #include <linux/vmalloc.h>
 #include <linux/set_memory.h>
 #include <linux/slab.h>
+#include <linux/pci-p2pdma.h>
 #include "direct.h"
 
 /*