Am 16.12.24 um 10:54 schrieb Wei Lin Guay:
From: Wei Lin Guay <wguay@xxxxxxxx> This is another attempt to revive the patches posted by Jason Gunthorpe and Vivek Kasireddy, at https://patchwork.kernel.org/project/linux-media/cover/0-v2-472615b3877e+28f7-vfio_dma_buf_jgg@xxxxxxxxxx/ https://lwn.net/Articles/970751/ In addition to the initial proposal by Jason, another promising application is exposing memory from an AI accelerator (bound to VFIO) to an RDMA device. This would allow the RDMA device to directly access the accelerator's memory, thereby facilitating direct data transactions between the RDMA device and the accelerator. Below is from the text/motivation from the orginal cover letter. 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. This series goes after the "Break up ioctl dispatch functions to one function per ioctl" series.
Yeah that sounds like it should work. But where is the rest of the series, I only see the cover letter?
v2: - Name the new file dma_buf.c - Restore orig_nents before freeing - Fix reversed logic around priv->revoked - Set priv->index - Rebased on v2 "Break up ioctl dispatch functions" v1: https://lore.kernel.org/r/0-v1-9e6e1739ed95+5fa-vfio_dma_buf_jgg@xxxxxxxxxx Cc: linux-rdma@xxxxxxxxxxxxxxx Cc: Oded Gabbay <ogabbay@xxxxxxxxxx> Cc: Christian König <christian.koenig@xxxxxxx> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> Cc: Leon Romanovsky <leon@xxxxxxxxxx> Cc: Maor Gottlieb <maorg@xxxxxxxxxx> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Jason Gunthorpe (3): vfio: Add vfio_device_get() dma-buf: Add dma_buf_try_get()
That is usually a no-go. We have rejected adding dma_buf_try_get() multiple times.
Please explain *exactly* what you need that for and how you protect against races with tearndown.
Regards, Christian.
vfio/pci: Allow MMIO regions to be exported through dma-buf Wei Lin Guay (1): vfio/pci: Allow export dmabuf without move_notify from importer drivers/vfio/pci/Makefile | 1 + drivers/vfio/pci/dma_buf.c | 291 +++++++++++++++++++++++++++++ drivers/vfio/pci/vfio_pci_config.c | 8 +- drivers/vfio/pci/vfio_pci_core.c | 44 ++++- drivers/vfio/pci/vfio_pci_priv.h | 30 +++ drivers/vfio/vfio_main.c | 1 + 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, 405 insertions(+), 8 deletions(-) create mode 100644 drivers/vfio/pci/dma_buf.c -- 2.43.5
