Parameter help, Using sr-iov with emulex devices, Advisory – Dell Emulex Family of Adapters User Manual

Page 620

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Emulex Drivers for Windows User Manual

P010077-01A Rev. A

3. Configuration

NIC Driver Configuration

620

3. The program provides a list of available registry parameters to modify or query.

Type either the number of the corresponding option or a substring in the parameter

name. The substring must uniquely identify the parameter or occfg will display all

potential options.

4. To apply the parameters, select the menu item to exit and reload the drivers.

Pressing control -c at any point may leave modifications in the registry, but the

driver does not use the new parameters until is reloaded.

Parameter Help

In interactive mode, setting a parameter will display help text and information

regarding the legal values for each parameter. This information can be dumped for all

parameters by specifying the -h option.
The following is an example help text for the RSS parameter:

RSS:

Receive Side Scaling (RSS) scales receive processing over multiple

CPUs in parallel. This scaling typically improves application

performance; however, it tends to increase CPU usage on low end

machines.

RSS is only supported on two primary adapters per device. It will

appear disabled for additional PCI functions in blade server

configurations.

RSS requires Windows 2008 and later.

Registry Key: *RSS

Default Value : 1 (Enable)

Valid Values :

0 = Disable

1 = Enable

Using SR-IOV with Emulex Devices

Advisory

OCe11100-series adapters may have an issue recovering from the corrupted use of

SR-IOV. Assigning an SR-IOV device to a virtual machine could leave the system

vulnerable and lead to instability. It is strongly recommended that you assign SR-IOV

devices only to virtual machines that run trusted workloads, or consider disabling

SR-IOV.
This advisory is highlighting a use case where a “rogue” [non-Emulex] digitally signed

driver is installed by the system administrator on a virtual machine. It is then possible

for that rogue driver to crash an OCe11100-series networking adapter. While there are

many benefits to using SR-IOV with virtualized workloads, these benefits should be

weighed against the potential risks in doing so. As an example, see the Microsoft

TechNet Blog cited in the link below where the benefits and usage of the Windows

Server 2012 Hyper-V switch versus NIC SR-IOV are noted:

http://www.emulex.com/downloads/sr-iov/

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