RE: [PATCH v2 1/9] PCI/P2PDMA: Add CONFIG_PCI_P2PDMA_CORE

[Tian, Kevin]

> From: Matt Evans <mattev@xxxxxxxx>
> Sent: Wednesday, May 27, 2026 6:23 PM
> 
> 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
> 
> Other code (such as vfio-pci) depends 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 which contains the
> basic provider functionality to make it available even if the
> CONFIG_PCI_P2PDMA feature is disabled or unavailable due to
> !CONFIG_ZONE_DEVICE.  Users such as vfio-pci can enable their own P2P
> features based off the original CONFIG_PCI_P2PDMA (available when
> CONFIG_ZONE_DEVICE is set).
> 
> Signed-off-by: Matt Evans <mattev@xxxxxxxx>

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