Intel Ethernet X520 10GbE Dual Port KX4 Mezz User Manual page 101

Rx Page Allocation Errors
Page allocation failure order: 0 errors may occur under stress with kernels 2.6.25 and above. This is caused by the way
the Linux kernel reports this stressed condition.
LRO and iSCSI Incompatibility
LRO is incompatible with iSCSI target or initiator traffic. A panic may occur when iSCSI traffic is received through the
ixgbe driver with LRO enabled. To avoid this issue, the driver should be built and installed with the following:
# make CFLAGS_EXTRA=-DIXGBE_NO_LRO install
DCB: Generic Segmentation Offload Enabled Causes Bandwidth Allocation Issues
In order for DCB to work correctly, GSO (Generic Segmentation Offload aka software TSO) must be disabled using eth-
tool. By default since the hardware supports TSO (hardware offload of segmentation) GSO will not be running. The
GSO state can be queried with ethtool using ethtool -k ethX.
When Using 82598-based network connections, ixgbe Driver Only Supports 16
Queues on a Platform with More than 16 Cores
Due to known hardware limitations, RSS can only filter in a maximum of 16 receive queues.
82599-based network connections support up to 64 queues.
Disable GRO When Routing/Bridging
Due to a known kernel issue, GRO must be turned off when routing/bridging. GRO can be turned off via ethtool.
ethtool -K ethX gro off
where ethX is the Ethernet interface you're trying to modify.
Lower than Expected Performance on Dual Port and Quad Port 10 Gigabit Ethernet
Devices
Some PCIe x8 slots are actually configured as x4 slots. These slots have insufficient bandwidth for full 10Gbe line rate
with dual port and quad port 10GbE devices. In addition, if you put a PCIe Gen 3-capable adapter into a PCIe Gen 2
slot, you can not get full bandwidth. The driver can detect this situation and will write the following message in the sys-
tem log: "PCI Express bandwidth available for this card is not sufficient for optimal performance. For optimal per-
formance a x8 PCI Express slot is required."
If this error occurs, moving your adapter to a true x8 slot will resolve the issue.
ethtool May Incorrectly Display SFP+ Fiber Module as Direct Attached Cable
Due to kernel limitations, port type can only be correctly displayed on kernel 2.6.33 or greater.
Running ethtool -t ethX Command Causes Break between PF and Test Client
When there are active VFs, "ethtool -t" will only run the link test. The driver will also log in syslog that VFs should be
shut down to run a full diagnostics test.
Enabling SR-IOV in a 32-bit or 64-bit Microsoft* Windows* Server 2008/R2 Guest OS
Using Intel® X540-based 10GbE Controller or Intel® 82599-based 10GbE Controller
Under KVM
KVM Hypervisor/VMM supports direct assignment of a PCIe device to a VM. This includes traditional PCIe devices, as
well as SR-IOV-capable devices using Intel X540-based and 82599-based controllers.