kernel/include/linux/pci-p2pdma.h, branch linux-rolling-stable

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

2025-11-20T19:02:00Z

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 Tested-by: Nicolin Chen Signed-off-by: Leon Romanovsky Acked-by: Ankit Agrawal Link: https://lore.kernel.org/r/20251120-dmabuf-vfio-v9-4-d7f71607f371@nvidia.com Signed-off-by: Alex Williamson

PCI/P2PDMA: Refactor to separate core P2P functionality from memory allocation

2025-11-20T19:01:52Z

Refactor the PCI P2PDMA subsystem to separate the core peer-to-peer DMA functionality from the optional memory allocation layer. This creates a two-tier architecture: The core layer provides P2P mapping functionality for physical addresses based on PCI device MMIO BARs and integrates with the DMA API for mapping operations. This layer is required for all P2PDMA users. The optional upper layer provides memory allocation capabilities including gen_pool allocator, struct page support, and sysfs interface for user space access. This separation allows subsystems like DMABUF to use only the core P2P mapping functionality without the overhead of memory allocation features they don't need. The core functionality is now available through the new pcim_p2pdma_provider() function that returns a p2pdma_provider structure. Tested-by: Alex Mastro Tested-by: Nicolin Chen Signed-off-by: Leon Romanovsky Acked-by: Ankit Agrawal Link: https://lore.kernel.org/r/20251120-dmabuf-vfio-v9-3-d7f71607f371@nvidia.com Signed-off-by: Alex Williamson

PCI/P2PDMA: Simplify bus address mapping API

2025-11-20T19:01:41Z

Update the pci_p2pdma_bus_addr_map() function to take a direct pointer to the p2pdma_provider structure instead of the pci_p2pdma_map_state. This simplifies the API by removing the need for callers to extract the provider from the state structure. The change updates all callers across the kernel (block layer, IOMMU, DMA direct, and HMM) to pass the provider pointer directly, making the code more explicit and reducing unnecessary indirection. This also removes the runtime warning check since callers now have direct control over which provider they use. Tested-by: Alex Mastro Tested-by: Nicolin Chen Signed-off-by: Leon Romanovsky Acked-by: Ankit Agrawal Link: https://lore.kernel.org/r/20251120-dmabuf-vfio-v9-2-d7f71607f371@nvidia.com Signed-off-by: Alex Williamson

PCI/P2PDMA: Separate the mmap() support from the core logic

2025-11-20T19:00:47Z

Currently the P2PDMA code requires a pgmap and a struct page to function. The was serving three important purposes: - DMA API compatibility, where scatterlist required a struct page as input - Life cycle management, the percpu_ref is used to prevent UAF during device hot unplug - A way to get the P2P provider data through the pci_p2pdma_pagemap The DMA API now has a new flow, and has gained phys_addr_t support, so it no longer needs struct pages to perform P2P mapping. Lifecycle management can be delegated to the user, DMABUF for instance has a suitable invalidation protocol that does not require struct page. Finding the P2P provider data can also be managed by the caller without need to look it up from the phys_addr. Split the P2PDMA code into two layers. The optional upper layer, effectively, provides a way to mmap() P2P memory into a VMA by providing struct page, pgmap, a genalloc and sysfs. The lower layer provides the actual P2P infrastructure and is wrapped up in a new struct p2pdma_provider. Rework the mmap layer to use new p2pdma_provider based APIs. Drivers that do not want to put P2P memory into VMA's can allocate a struct p2pdma_provider after probe() starts and free it before remove() completes. When DMA mapping the driver must convey the struct p2pdma_provider to the DMA mapping code along with a phys_addr of the MMIO BAR slice to map. The driver must ensure that no DMA mapping outlives the lifetime of the struct p2pdma_provider. The intended target of this new API layer is DMABUF. There is usually only a single p2pdma_provider for a DMABUF exporter. Most drivers can establish the p2pdma_provider during probe, access the single instance during DMABUF attach and use that to drive the DMA mapping. DMABUF provides an invalidation mechanism that can guarantee all DMA is halted and the DMA mappings are undone prior to destroying the struct p2pdma_provider. This ensures there is no UAF through DMABUFs that are lingering past driver removal. The new p2pdma_provider layer cannot be used to create P2P memory that can be mapped into VMA's, be used with pin_user_pages(), O_DIRECT, and so on. These use cases must still use the mmap() layer. The p2pdma_provider layer is principally for DMABUF-like use cases where DMABUF natively manages the life cycle and access instead of vmas/pin_user_pages()/struct page. In addition, remove the bus_off field from pci_p2pdma_map_state since it duplicates information already available in the pgmap structure. The bus_offset is only used in one location (pci_p2pdma_bus_addr_map) and is always identical to pgmap->bus_offset. Signed-off-by: Jason Gunthorpe Tested-by: Alex Mastro Tested-by: Nicolin Chen Signed-off-by: Leon Romanovsky Acked-by: Ankit Agrawal Link: https://lore.kernel.org/r/20251120-dmabuf-vfio-v9-1-d7f71607f371@nvidia.com Signed-off-by: Alex Williamson

PCI/P2PDMA: Reduce scope of pci_has_p2pmem()

2025-09-03T22:01:39Z

pci_has_p2pmem() is not used outside of p2pdma.c, and there is no need to export it for use by modules. Signed-off-by: Leon Romanovsky Signed-off-by: Bjorn Helgaas Reviewed-by: Logan Gunthorpe Link: https://patch.msgid.link/d40f3f1decf54c9236bc38b48a6aae612a5c182f.1756900291.git.leon@kernel.org

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

2025-05-06T06:36:53Z

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 Reviewed-by: Logan Gunthorpe Acked-by: Bjorn Helgaas Tested-by: Jens Axboe Reviewed-by: Luis Chamberlain Reviewed-by: Lu Baolu Signed-off-by: Leon Romanovsky Signed-off-by: Marek Szyprowski

PCI/P2PDMA: Remove pci_p2pdma_[un]map_sg()

2022-07-26T11:28:08Z

This interface is superseded by support in dma_map_sg() which now supports heterogeneous scatterlists. There are no longer any users, so remove it. Signed-off-by: Logan Gunthorpe Acked-by: Bjorn Helgaas Reviewed-by: Jason Gunthorpe Reviewed-by: Max Gurtovoy Reviewed-by: Christoph Hellwig Signed-off-by: Christoph Hellwig

PCI/P2PDMA: Introduce pci_p2pdma_unmap_sg()

2019-08-16T13:41:26Z

Add pci_p2pdma_unmap_sg() to the two places that call pci_p2pdma_map_sg(). This is a prep patch to introduce correct mappings for p2pdma transactions that go through the root complex. Link: https://lore.kernel.org/r/20190730163545.4915-10-logang@deltatee.com Link: https://lore.kernel.org/r/20190812173048.9186-10-logang@deltatee.com Signed-off-by: Logan Gunthorpe Signed-off-by: Bjorn Helgaas Reviewed-by: Christoph Hellwig

PCI/P2PDMA: Add attrs argument to pci_p2pdma_map_sg()

2019-08-16T13:41:15Z

This is to match the dma_map_sg() API which this function will have to call in an future patch. Add a pci_p2pdma_map_sg_attrs() function and helper to call it with no attributes just like the dma_map_sg() function. Link: https://lore.kernel.org/r/20190730163545.4915-9-logang@deltatee.com Link: https://lore.kernel.org/r/20190812173048.9186-9-logang@deltatee.com Signed-off-by: Logan Gunthorpe Signed-off-by: Bjorn Helgaas Reviewed-by: Christoph Hellwig

PCI/P2PDMA: Introduce configfs/sysfs enable attribute helpers

2018-10-17T17:18:17Z

Users of the P2PDMA infrastructure will typically need a way for the user to tell the kernel to use P2P resources. Typically this will be a simple on/off boolean operation but sometimes it may be desirable for the user to specify the exact device to use for the P2P operation. Add new helpers for attributes which take a boolean or a PCI device. Any boolean as accepted by strtobool() turn P2P on or off (such as 'y', 'n', '1', '0', etc). Specifying a full PCI device name/BDF will select the specific device. Signed-off-by: Logan Gunthorpe Signed-off-by: Bjorn Helgaas Reviewed-by: Christoph Hellwig