Re: [RFC PATCH 0/5] vfio/pci: Support ZONE_DEVICE-backed P2P Registration

[Jason Gunthorpe]

On Wed, Jun 10, 2026 at 03:18:48PM +0000, Pranjal Shrivastava wrote:

> Users utilize the standard sysfs p2pmem/allocate interface for managing
> memory slices once a BAR is registered.

I'm shocked someone wants to use API, what are you expecting to do
with it??

> An alternative implementation has been explored which integrates with the
> ongoing VFIO DMABUF-mmap refactor [1]. In that approach, rather than
> registering a BAR as a system-wide P2P provider, VFIO optionally
> allocates ZONE_DEVICE pages only for specifically exported DMABUFs via a
> new VFIO_DMA_BUF_FLAG_ALLOC_STRUCT_PAGES flag.

That's probably more sensible but you can't have a DMABUF mmap
actually install non-special memory. The native vfio mmap still can,
but not mmap on the dmabuf fd. That's still workable, just keep in
mind.

What do you even intend to do with this? With the new work to tie
dmabuf directly into io_uring I really wonder if this is worth doing
for VFIO?

Jason