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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: Alex Mastro <amastro@fb.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Acked-by: Ankit Agrawal <ankita@nvidia.com>
Link: https://lore.kernel.org/r/20251120-dmabuf-vfio-v9-4-d7f71607f371@nvidia.com
Signed-off-by: Alex Williamson <alex@shazbot.org>
This commit is contained in:
Leon Romanovsky 2025-11-20 11:28:23 +02:00 committed by Alex Williamson
parent 372d6d1b8a
commit 395698bd2c
2 changed files with 58 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
drivers/pci/p2pdma.c
View File

@ -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);

85
include/linux/pci-p2pdma.h
View File

@ -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;