Re: [PATCH 4/9] vfio/pci: Convert BAR mmap() to use a DMABUF

Jason Gunthorpe
2026-05-04T07:40:48Z

On Fri, May 01, 2026 at 04:19:15PM -0600, Alex Williamson wrote:

> Exporting dma-bufs from vfio-pci is a feature, but mmap of MMIO BARs is
> a legacy requirement. That legacy requirement now depends on
> PCI_P2PDMA, which depends on 64BIT and ZONE_DEVICE.

That should be split up now, Leon missed it when he added the new
APIs that didn't require ZONE_DEVICE..

> ZONE_DEVICE is harder, it seems like it's possible there could be
> minimal 64-bit custom kernel configs where vfio-pci currently works
> without ZONE_DEVICE.

Several VFIO using arches cannot tolerate ZONE_DEVICE, IIRC, so we
must avoid that dependency.

I think if we clean up the kconfig for p2p so it is always available
it would be no problem to keep this patch relying on it, but that
needs to either be done in this series or before it

Jason