Am 17.08.22 um 18:11 schrieb Jason Gunthorpe:
dma-buf has become a way to safely acquire a handle to non-struct page memory that can still have lifetime controlled by the exporter. Notably RDMA can now import dma-buf FDs and build them into MRs which allows for PCI P2P operations. Extend this to allow vfio-pci to export MMIO memory from PCI device BARs. This 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. I imagine this dmabuf approach to be usable by iommufd as well for generic and safe P2P mappings.
In general looks good to me, but we really need to get away from using sg_tables for this here.
The only thing I'm not 100% convinced of is dma_buf_try_get(), I've seen this incorrectly used so many times that I can't count them any more.
Would that be somehow avoidable? Or could you at least explain the use case a bit better.
Thanks, Christian.
This series goes after the "Break up ioctl dispatch functions to one function per ioctl" series. This is on github: https://github.com/jgunthorpe/linux/commits/vfio_dma_buf Jason Gunthorpe (4): dma-buf: Add dma_buf_try_get() vfio: Add vfio_device_get() vfio_pci: Do not open code pci_try_reset_function() vfio/pci: Allow MMIO regions to be exported through dma-buf drivers/vfio/pci/Makefile | 1 + drivers/vfio/pci/vfio_pci_config.c | 22 ++- drivers/vfio/pci/vfio_pci_core.c | 33 +++- drivers/vfio/pci/vfio_pci_dma_buf.c | 265 ++++++++++++++++++++++++++++ drivers/vfio/pci/vfio_pci_priv.h | 24 +++ drivers/vfio/vfio_main.c | 3 +- include/linux/dma-buf.h | 13 ++ include/linux/vfio.h | 6 + include/linux/vfio_pci_core.h | 1 + include/uapi/linux/vfio.h | 18 ++ 10 files changed, 364 insertions(+), 22 deletions(-) create mode 100644 drivers/vfio/pci/vfio_pci_dma_buf.c base-commit: 385f0411fcd2780b5273992832cdc8edcd5b8ea9
