> This series extends the VFIO PCI subsystem to support exporting MMIO > regions from PCI device BARs as dma-buf objects, enabling safe sharing of > non-struct page memory with controlled lifetime management. This allows RDMA > and other subsystems to import dma-buf FDs and build them into memory regions > for PCI P2P operations. > > The series supports a use case for SPDK where a NVMe device will be > owned by SPDK through VFIO but interacting with a RDMA device. The RDMA > device may directly access the NVMe CMB or directly manipulate the NVMe > device's doorbell using PCI P2P. > > However, as a general mechanism, it can support many other scenarios with > VFIO. This dmabuf approach can be usable by iommufd as well for generic > and safe P2P mappings. > > In addition to the SPDK use-case mentioned above, the capability added > in this patch series can also be useful when a buffer (located in device > memory such as VRAM) needs to be shared between any two dGPU devices or > instances (assuming one of them is bound to VFIO PCI) as long as they > are P2P DMA compatible. > > The implementation provides a revocable attachment mechanism using dma-buf > move operations. MMIO regions are normally pinned as BARs don't change > physical addresses, but access is revoked when the VFIO device is closed > or a PCI reset is issued. This ensures kernel self-defense against > potentially hostile userspace. > > The series includes significant refactoring of the PCI P2PDMA subsystem > to separate core P2P functionality from memory allocation features, > making it more modular and suitable for VFIO use cases that don't need > struct page support. > > ----------------------------------------------------------------------- > The series is based originally on > https://lore.kernel.org/all/[email protected]/ > but heavily rewritten to be based on DMA physical API. > ----------------------------------------------------------------------- > The WIP branch can be found here: > https://git.kernel.org/pub/scm/linux/kernel/git/leon/linux-rdma.git/log/?h=dmabuf-vfio-v9
Acked-by: Ankit Agrawal <[email protected]>
