vfio/pci: Add vfio_pci_dma_buf_iommufd_map()

This function is used to establish the "private interconnect" between the
VFIO DMABUF exporter and the iommufd DMABUF importer. This is intended to
be a temporary API until the core DMABUF interface is improved to natively
support a private interconnect and revocable negotiation.

This function should only be called by iommufd when trying to map a
DMABUF. For now iommufd will only support VFIO DMABUFs.

The following improvements are needed in the DMABUF API to generically
support more exporters with iommufd/kvm type importers that cannot use the
DMA API:

 1) Revoke semantics. VFIO needs to be able to prevent access to the MMIO
    during FLR, and so it will use dma_buf_move_notify() to prevent
    access. iommmufd does not support fault handling so it cannot
    implement the full move_notify. Instead if revoke is negotiated the
    exporter promises not to use move_notify() unless the importer can
    experiance failures. iommufd will unmap the dmabuf from the iommu page
    tables while it is revoked.

 2) Private interconnect negotiation. iommufd will only be able to map
    a "private interconnect" that provides a phys_addr_t and a
    struct p2pdma_provider * to describe the memory. It cannot use a DMA
    mapped scatterlist since it is directly calling iommu_map().

 3) NULL device during dma_buf_dynamic_attach(). Since iommufd doesn't use
    the DMA API it doesn't have a DMAable struct device to pass here.

Link: https://patch.msgid.link/r/1-v2-b2c110338e3f+5c2-iommufd_dmabuf_jgg@nvidia.com
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Shuai Xue <xueshuai@linux.alibaba.com>
Acked-by: Alex Williamson <alex@shazbot.org>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

0 files changed, 0 insertions, 0 deletions