# lspci -vvv -s 04:00.0
04:00.0 Ethernet controller: Intel Corporation Ethernet 10G 2P X520 Adapter (rev 01)
...

 Capabilities: [160 v1] Single Root I/O Virtualization (SR-IOV)
IOVCap: Migration-, Interrupt Message Number: 000
IOVCtl: Enable- Migration- Interrupt- MSE- ARIHierarchy+
IOVSta: Migration-
** Initial VFs: 64, Total VFs: 64**, Number of VFs: 0, Function Dependency Link: 00
VF offset: 128, stride: 2, Device ID: 10ed
Supported Page Size: 00000553, System Page Size: 00000001
Region 0: Memory at 0000000094400000 (64-bit, prefetchable)
Region 3: Memory at 0000000094500000 (64-bit, prefetchable)
VF Migration: offset: 00000000, BIR: 0
Kernel driver in use: ixgbe
Kernel modules: ixgbe

# cat /sys/class/net/enp4s0f0/device/sriov_totalvfs
63

# echo 64 > /sys/class/net/enp4s0f0/device/sriov_numvfs
-bash: echo: write error: Numerical result out of range
# echo 63 > /sys/class/net/enp4s0f0/device/sriov_numvfs
# cat /sys/class/net/enp4s0f0/device/sriov_numvfs
63

The lspci command says the Total VFs supported is 64, while in the file "sriov_totalvfs"  says it's 63.
And the sriov_numvfs file will take precedence.

Why are the numbers different?  Just a little curious.

Thank you!

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Best Regards,
Yalan Zhang
IRC: yalzhang