On Sat, 28 Jan 2017 13:28:25 +0200 Kevin Wilson <wkevils@xxxxxxxxx> wrote: > Hello, > I had noticed that whenever I create virtual function on Nic devices, > the numbering scheme is the same: > the the last digit of first VF is .0, of the second one is .2, the > third is .4, and so on; and no odd number are used. > > For example, with Intel IXGBE nic, we have: > > > echo 4 > /sys/bus/pci/devices/0000:06:00.0/sriov_numvfs > > lspci | grep "Virtual Function" > 06:10.0 Ethernet controller: Intel Corporation 82599 Ethernet > Controller Virtual Function (rev 01) > 06:10.2 Ethernet controller: Intel Corporation 82599 Ethernet > Controller Virtual Function (rev 01) > 06:10.4 Ethernet controller: Intel Corporation 82599 Ethernet > Controller Virtual Function (rev 01) > 06:10.6 Ethernet controller: Intel Corporation 82599 Ethernet > Controller Virtual Function (rev 01) > > Does anybody know what is the reason that odd numbers are not used ? > are they kept for something else ? > For example, why don't we get : 06:10.0,06:10.1,06:10.2,06:10.3 in this case ? The SR-IOV capability defines the offset and stride for VFs. On Intel devices the stride is typically 2, so you get this even number VF layout, but only on the even numbered PF. The odd numbered PF typically fills in the gaps, creating only odd numbered VFs. In any case, it's the card vendor that defines the VF layout via the SR-IOV capability parameters. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
