RE: [PATCH v5 2/9] PCI/P2PDMA: Add CONFIG_PCI_P2PDMA_CORE

[Tian, Kevin]

> From: Matt Evans <matt@xxxxxxxxxx>
> Sent: Thursday, July 16, 2026 1:47 AM
> 
> 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 vfio-pci commit will rely 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), satisfying (1).
> 
> Then, when the original CONFIG_PCI_P2PDMA is set, drivers have access
> to the additional P2P features of (2).  This still depends on
> CONFIG_ZONE_DEVICE.
> 
> Signed-off-by: Matt Evans <matt@xxxxxxxxxx>
> Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Reviewed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>