This is an attempt to revive the patches posted by Jason Gunthorpe at: https://patchwork.kernel.org/project/linux-media/cover/0-v2-472615b3877e+28f7-vfio_dma_buf_jgg@xxxxxxxxxx/ Here is the cover letter text from Jason's original series: "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 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 original series has been rebased and augmented to support creation of the dmabuf from multiple ranges of a region. Changelog: v2 -> v3: - Rebase onto 6.14-rc5 - Drop the mmap handler given that it is undesirable in some use-cases - Rename the file dma_buf.c to vfio_pci_dmabuf.c to be consistent with other files in vfio/pci directory v1 -> v2: - Rebase on 6.10-rc4 - Update the copyright year in dma_buf.c (Zhu Yanjun) - Check the revoked flag during mmap() and also revoke the mappings as part of move when access to the MMIO space is disabled (Alex) - Include VM_ALLOW_ANY_UNCACHED and VM_IO flags for mmap (Alex) - Fix memory leak of ranges when creation of priv fails (Alex) - Check return value of vfio_device_try_get_registration() (Alex) - Invoke dma_buf move for runtime PM and FLR cases as well (Alex) - Add a separate patch to have all the feature functions take the core device pointer instead of the main device ptr (Alex) - Use the regular DMA APIs (that were part of original series) instead of PCI P2P DMA APIs while mapping the dma_buf (Jason) - Rename the region's ranges from p2p_areas to dma_ranges (Jason) - Add comments in vfio_pci_dma_buf_move() to describe how the locking is expected to work (Jason) This series is available at: https://gitlab.freedesktop.org/Vivek/drm-tip/-/commits/vfio_dmabuf_v3 along with additional patches (needed for testing) for Qemu here: https://gitlab.freedesktop.org/Vivek/qemu/-/commits/vfio_dmabuf_3 This series is tested using the following method: - Run Qemu with the following relevant options: qemu-system-x86_64 -m 4096m .... -device vfio-pci,host=0000:03:00.1 -device virtio-vga,max_outputs=1,blob=true,xres=1920,yres=1080 -display gtk,gl=on -object memory-backend-memfd,id=mem1,size=4096M -machine memory-backend=mem1 ... - Run upstream Weston with following options in the Guest VM: ./weston --drm-device=card1 --additional-devices=card0 where card1 is a dGPU (assigned to vfio-pci and using xe driver in Guest VM), card0 is virtio-gpu. - Or run Mutter with Wayland backend in the Guest VM with the dGPU designated as the primary Cc: Jason Gunthorpe <jgg@xxxxxxxxxx> Cc: Leon Romanovsky <leonro@xxxxxxxxxx> Cc: Christian König <christian.koenig@xxxxxxx> Cc: Simona Vetter <simona.vetter@xxxxxxxx> Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx> Cc: Alex Williamson <alex.williamson@xxxxxxxxxx> Cc: Yishai Hadas <yishaih@xxxxxxxxxx> Cc: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx> Cc: Kevin Tian <kevin.tian@xxxxxxxxx> Cc: Wei Lin Guay <wguay@xxxxxxxx> Cc: Xu Yilun <yilun.xu@xxxxxxxxxxxxxxx> Vivek Kasireddy (3): vfio: Export vfio device get and put registration helpers vfio/pci: Share the core device pointer while invoking feature functions 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 | 50 ++-- drivers/vfio/pci/vfio_pci_dmabuf.c | 359 +++++++++++++++++++++++++++++ drivers/vfio/pci/vfio_pci_priv.h | 23 ++ drivers/vfio/vfio_main.c | 2 + include/linux/vfio.h | 2 + include/linux/vfio_pci_core.h | 1 + include/uapi/linux/vfio.h | 25 ++ 9 files changed, 463 insertions(+), 22 deletions(-) create mode 100644 drivers/vfio/pci/vfio_pci_dmabuf.c -- 2.48.1
