Bo Chen 87992c77c1 vmm: Introduce option --platform vfio_p2p_dma=on|off ...

Add a user-configurable option to control whether VFIO device MMIO BAR
regions are DMA-mapped into the host IOMMU address space.

This mapping is required for peer-to-peer DMA between devices (e.g.
NVLink, RDMA NIC accessing GPU VRAM). However, iommufd on upstream
kernels does not support mapping device MMIO pages (VM_PFNMAP), causing
IOMMU_IOAS_MAP to fail with -EFAULT. Kernels with the NVIDIA PFNMAP
workaround or future kernels with DMABUF-based mapping
(IOMMU_IOAS_MAP_FILE) handle this correctly.

The option defaults to `on` to preserve existing behavior. Users on
vanilla kernels using iommufd should set `vfio_p2p_dma=off` to skip
MMIO BAR DMA mapping.

A validation check ensures that `x_nv_gpudirect_clique` (which depends
on P2P DMA) cannot be used when `vfio_p2p_dma=off`.

Signed-off-by: Bo Chen <bchen@crusoe.ai>

2026-04-10 22:55:38 +00:00

..

src

vmm: Introduce option --platform vfio_p2p_dma=on|off

2026-04-10 22:55:38 +00:00

Cargo.toml

misc: make MSRV workspace-wide for cloud-hypervisor dependencies

2026-03-13 01:30:25 +00:00