CONFIG_PCI_P2PDMA: PCI peer-to-peer transfer support

General informations

The Linux kernel configuration item CONFIG_PCI_P2PDMA:

• prompt: PCI peer-to-peer transfer support
• type: bool
• depends on: ( CONFIG_ZONE_DEVICE ) && ( CONFIG_64BIT )
• defined in drivers/pci/Kconfig
• found in Linux kernels: 4.20, 5.0–5.19, 6.0–6.14, 6.15-rc+HEAD

Help text

Enables drivers to do PCI peer-to-peer transactions to and from BARs that are exposed in other devices that are the part of the hierarchy where peer-to-peer DMA is guaranteed by the PCI specification to work (ie. anything below a single PCI bridge).

Many PCIe root complexes do not support P2P transactions and it's hard to tell which support it at all, so at this time, P2P DMA transactions must be between devices behind the same root port.

Enabling this option will reduce the entropy of x86 KASLR memory regions. For example - on a 46 bit system, the entropy goes down from 16 bits to 15 bits. The actual reduction in entropy depends on the physical address bits, on processor features, kernel config (5 level page table) and physical memory present on the system.

If unsure, say N.

Hardware

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Sources

This page is automaticly generated with free (libre, open) software lkddb(see lkddb-sources).

The data is retrived from:

• Linux kernel
• Linux Kernel Driver DataBase (LKDDb)

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