[nvidia_stable-11.0] NVIDIA: SAUCE: WAR: hw/vfio: Retry dma_map to bypass PFNMAP#20
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The dma_map_file pathway doesn't fit into the kernel WAR that bypasses PFNMAP, resulting dma_map failures. Only the dma_map pathway could work. So retry with that upon a failure. Keep this WAR until the kernel WAR for PFNMAP is lifted. Signed-off-by: Nicolin Chen <nicolinc@nvidia.com> (cherry picked from commit faff92d https://github.com/nvmochs/QEMU/tree/stable101_smmuv3-accel-07212025_egm) [nathanc: Moved changes from hw/vfio/container-base.c to hw/vfio/container.c for 11.0 base] Signed-off-by: Nathan Chen <nathanc@nvidia.com>
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Summary
EGM uses file-backed guest RAM (/dev/egm*) which selects the vfio_container_dma_map() path in hw/vfio/container.c. When this mapping fails with kernels lacking dmabuf support, return a successful return value to move forward with the bypass PFNMAP WAR in place of dmabuf support: NVIDIA: SAUCE: WAR: iommufd/pages: Bypass PFNMAP. This patch is not required when dmabuf support is present.
Testing
Launch 4 GPU EGM VM on GB200 with linux-nvidia 6.17.0-1018-nvidia-64k, verify nvidia-smi and CUDA samples