Nvidia BlueField-3 - Bifurcated to Eight x4 PCIe

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Configuration Root Port Arm DPU PCIe Golden Fingers
Bifurcation
DPU PCIe Auxiliary
Connection Bifurcation
Default DPU Arm 1 x Gen 5.0/4.0 x16 PCIe
lanes as down-stream-port
1 x Gen 5.0/4.0 x16 PCIe
lanes as down-stream-port
Bifurcated to Eight x4 PCIe DPU Arm 4 x Gen 5.0/4.0 x4 PCIe
lanes as down-stream-port
4 x Gen 5.0/4.0 x4 PCIe
lanes as down-stream-port
Bifurcated to One x16 PCIe
and Eight x2 PCIe
DPU Arm 1 x Gen 5.0/4.0 x16 PCIe
lanes as down-stream-port
8 x Gen 5.0/4.0 x2 PCIe
lanes as down-stream-port
5.12.1 Bifurcated to Eight x4 PCIe
In this scenario, the x16 PCIe Goldfingers of the BlueField-3 DPU are bifurcated into four PCIe links,
where each link comprises x4 PCIe lanes, while the additional x16 PCIe lanes are accessible via the
Cabline CA-II Plus connector, bifurcated into four PCIe links, where each link comprises x4 PCIe
lanes.
As seen in the below visual representation of this configuration, the DPU’s Arm cores function as
Root Port of all devices connected to both the Gold Fingers and the Cabline CA-II Plus connector.
The required set of configurations to implement this bifurcation is outlined below.
mlxconfig -d <device> s PCI_BUS00_HIERARCHY_TYPE=2
mlxconfig -d <device> s PCI_BUS00_WIDTH=3
mlxconfig -d <device> s PCI_BUS00_SPEED=4
mlxconfig -d <device> s PCI_BUS02_HIERARCHY_TYPE=2
mlxconfig -d <device> s PCI_BUS02_WIDTH=3
mlxconfig -d <device> s PCI_BUS02_SPEED=4
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Important Notes:
mlxconfig can be configured either through the host in NIC Mode and DPU Mode, or
directly from the DPU’s Arm running OS.
This configuration is persistent even following resets and NIC firmware updates.