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Single Root I/O Virtualization (SR-IOV) device consumes more PCI bus numbers than required for enabled virtual functions (2039824)

Details

If a PCI Single Root I/O Virtualization (SR-IOV) device has multiple physical functions, and the virtual functions (VFs) for the device are initially enabled in a physical function (PF)  other than the lowest numbered PF in the device, ESXi fails to set the ARI_Capable_Hierarchy bit in the SR-IOV device.

This causes the SR-IOV device to consume more PCI bus numbers than the enabled virtual functions require. This condition affects the allocation of PCI bus number resources in the system.

The exact behavior is device-specific and also depends on the number of virtual functions being created. Generally, if the number of VFs being created is less than eight (8), the correct number of VFs might be created. If the number of VFs is greater than eight (8), some number less than eight or no VFs might be created.

As an example, when you use the ixgbe driver associated with the Intel 82599 10Gb dual-ported NIC (for which the max_vfs parameter is specific), if the max_vfs parameter is set to 0,n n VFs are created in PF1.  If the VFs are created in a PF other than the lowest numbered one, ESXi will not set the ARI_Capable_Hierarchy bit.  If the device requires this bit to provision VFs with proper PCI routing IDs, the desired number of VFs might not be created.

Solution

This is a known issue affecting ESXi 5.1. This article will be updated as information becomes available.

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To work around this issue, enable virtual functions first in the lowest-numbered physical function of the SR-IOV device.

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