Commit 395698bd authored by Leon Romanovsky's avatar Leon Romanovsky Committed by Alex Williamson
Browse files

PCI/P2PDMA: Provide an access to pci_p2pdma_map_type() function 



Provide an access to pci_p2pdma_map_type() function to allow subsystems
to determine the appropriate mapping type for P2PDMA transfers between
a provider and target device.

The pci_p2pdma_map_type() function is the core P2P layer version of
the existing public, but struct page focused, pci_p2pdma_state()
function. It returns the same result. It is required to use the p2p
subsystem from drivers that don't use the struct page layer.

Like __pci_p2pdma_update_state() it is not an exported function. The
idea is that only subsystem code will implement mapping helpers for
taking in phys_addr_t lists, this is deliberately not made accessible
to every driver to prevent abuse.

Following patches will use this function to implement a shared DMA
mapping helper for DMABUF.

Tested-by: default avatarAlex Mastro <amastro@fb.com>
Tested-by: default avatarNicolin Chen <nicolinc@nvidia.com>
Signed-off-by: default avatarLeon Romanovsky <leonro@nvidia.com>
Acked-by: default avatarAnkit Agrawal <ankita@nvidia.com>
Link: https://lore.kernel.org/r/20251120-dmabuf-vfio-v9-4-d7f71607f371@nvidia.com


Signed-off-by: default avatarAlex Williamson <alex@shazbot.org>
parent 372d6d1b

drivers/pci/p2pdma.c

+12 −2
Original line number Diff line number Diff line
@@ -1060,8 +1060,18 @@ void pci_p2pmem_publish(struct pci_dev *pdev, bool publish) 
}

EXPORT_SYMBOL_GPL(pci_p2pmem_publish);



static enum pci_p2pdma_map_type

pci_p2pdma_map_type(struct p2pdma_provider *provider, struct device *dev)

/**

 * pci_p2pdma_map_type - Determine the mapping type for P2PDMA transfers

 * @provider: P2PDMA provider structure

 * @dev: Target device for the transfer

 *

 * Determines how peer-to-peer DMA transfers should be mapped between

 * the provider and the target device. The mapping type indicates whether

 * the transfer can be done directly through PCI switches or must go

 * through the host bridge.

 */

enum pci_p2pdma_map_type pci_p2pdma_map_type(struct p2pdma_provider *provider,

					     struct device *dev)

{

	enum pci_p2pdma_map_type type = PCI_P2PDMA_MAP_NOT_SUPPORTED;

	struct pci_dev *pdev = to_pci_dev(provider->owner);

include/linux/pci-p2pdma.h

+46 −39
Original line number Diff line number Diff line
@@ -26,6 +26,45 @@ struct p2pdma_provider { 
	u64 bus_offset;

};



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,

};



#ifdef CONFIG_PCI_P2PDMA

int pcim_p2pdma_init(struct pci_dev *pdev);

struct p2pdma_provider *pcim_p2pdma_provider(struct pci_dev *pdev, int bar);
@@ -45,6 +84,8 @@ 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,

			       bool use_p2pdma);

enum pci_p2pdma_map_type pci_p2pdma_map_type(struct p2pdma_provider *provider,

					     struct device *dev);

#else /* CONFIG_PCI_P2PDMA */

static inline int pcim_p2pdma_init(struct pci_dev *pdev)

{
@@ -106,6 +147,11 @@ static inline ssize_t pci_p2pdma_enable_show(char *page, 
{

	return sprintf(page, "none\n");

}

static inline enum pci_p2pdma_map_type

pci_p2pdma_map_type(struct p2pdma_provider *provider, struct device *dev)

{

	return PCI_P2PDMA_MAP_NOT_SUPPORTED;

}

#endif /* CONFIG_PCI_P2PDMA */
@@ -120,45 +166,6 @@ 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 p2pdma_provider *mem;

	enum pci_p2pdma_map_type map;