On Wed, Jun 10, 2026 at 04:43:15PM +0100, Matt Evans wrote:

The P2PDMA code currently provides two features under the same CONFIG_PCI_P2PDMA option:

1. Locate providers via pcim_p2pdma_provider()
2. Manage actual P2P DMA

Some drivers (such as vfio-pci) depend on 1, without having a hard dependency on 2.

A future commit expands the use of DMABUF in vfio-pci for non-P2P scenarios, relying on pcim_p2pdma_provider() always being present. If that depended on CONFIG_PCI_P2PDMA, it would make vfio-pci only available if CONFIG_ZONE_DEVICE is present (e.g. 64-bit systems), even when P2P is not needed.

To resolve this, introduce CONFIG_PCI_P2PDMA_CORE and refactor the basic provider functionality into a new p2pdma_core.c file. This is available even if the CONFIG_PCI_P2PDMA feature is disabled (or unavailable due to !CONFIG_ZONE_DEVICE). Then, drivers can enable any additional P2P features with the original CONFIG_PCI_P2PDMA (available when CONFIG_ZONE_DEVICE is set).

Signed-off-by: Matt Evans matt@ozlabs.org

MAINTAINERS | 2 +- drivers/pci/Kconfig | 10 ++-- drivers/pci/Makefile | 1 + drivers/pci/p2pdma.c | 109 ++-------------------------------- drivers/pci/p2pdma.h | 29 +++++++++ drivers/pci/p2pdma_core.c | 118 +++++++++++++++++++++++++++++++++++++ include/linux/pci-p2pdma.h | 24 ++++---- include/linux/pci.h | 2 +- 8 files changed, 174 insertions(+), 121 deletions(-) create mode 100644 drivers/pci/p2pdma.h create mode 100644 drivers/pci/p2pdma_core.c

Thanks, Reviewed-by: Leon Romanovsky leonro@nvidia.com