SR-IOV

SR-IOV, short for Single Root I/O Virtualization, is a PCI Express extended capability that makes one physical device appear as multiple virtual devices. The physical device is the Physical Function, or PF. The virtual devices are Virtual Functions, or VFs. Each VF gets its own bus, device and function number, so it shows up as a separate PCI device that a hypervisor can hand to its own virtual machine. It is off by default. On Linux, writing a count to sriov_numvfs in sysfs turns VFs on.

On NVIDIA GPUs from the Ampere architecture onward, vGPU needs VT-d or IOMMU, SR-IOV and Alternative Routing ID Interpretation (ARI) all enabled in the BIOS. On a Linux KVM host, NVIDIA's sriov-manage script then enables the VFs, and a vGPU is created on a VF, one per VF. The VFs disappear after a host reboot or driver reload, so the script runs again. On the RTX PRO 6000 Blackwell Server Edition, profile DC-3Q allows 32 vGPUs of 3 GB each. Windows Server 2025 GPU partitioning uses the same interface.

Confirm the BIOS exposes SR-IOV, the IOMMU and ARI before buying a host for vGPU or GPU partitioning. Use passthrough instead when one VM needs the whole card.

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Last verified October 30, 2026.