What is the specific functionality of a PF(Physical Function)  in SR-IOV ? Also what is the difference between virtual function and a physical function ? Does the VF communicate with a PF during the transfer of a packet from the VM ?

Hi Ygkumar,

  Thank you for the post. 

1) The specific funtionality of a PF in SR-IOV is actually refers to the physical NIC that includes the full feature of the PCI-e functions, it is to configure and manage the SR-IOV. 
.You may refer to page 13 at 
 http://www.intel.com/content/www/us/en/pci-express/pci-sig-sr-iov-primer-sr-iov-technology-paper.html

2) The difference between virtual function and physical function as follow:
(based on page 13 of the website above) 

-Physical Functions (PFs): These are full PCIe functions that include the SR-IOV, Extended Capability. The capability is used to configure and manage the SR-IOV functionality. 
- Virtual Functions (VFs): These are ‘lightweight’ PCIe functions that contain the resources necessary for data movement but have a carefully minimized set of configuration resources (this is the virtual NIC) 


3) You may refer to page 12, the sample shows that the 3 virtual machines are directly accessing to dedicated resources within the ethernet controller without passing the PF.
 http://www.intel.com/content/www/us/en/pci-express/pci-sig-sr-iov-primer-sr-iov-technology-paper.html

Thanks,
wb
 

Hi Ygkumar,

 Good day. Please feel free to update me if further assistance needed?

rgds,
wb