Add some background documentation on netvsc device options and limitations. Signed-off-by: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx> --- Documentation/networking/netvsc.txt | 63 +++++++++++++++++++++++++++++++++++++ MAINTAINERS | 1 + 2 files changed, 64 insertions(+) create mode 100644 Documentation/networking/netvsc.txt diff --git a/Documentation/networking/netvsc.txt b/Documentation/networking/netvsc.txt new file mode 100644 index 000000000000..4ddb4e4b0426 --- /dev/null +++ b/Documentation/networking/netvsc.txt @@ -0,0 +1,63 @@ +Hyper-V network driver +====================== + +Compatibility +============= + +This driver is compatible with Windows Server 2012 R2, 2016 and +Windows 10. + +Features +======== + + Checksum offload + ---------------- + The netvsc driver supports checksum offload as long as the + Hyper-V host version does. Windows Server 2016 and Azure + support checksum offload for TCP and UDP for both IPv4 and + IPv6. Windows Server 2012 only supports checksum offload for TCP. + + Receive Side Scaling + -------------------- + Hyper-V supports receive side scaling. For TCP, packets are + distributed among available queues based on IP address and port + number. Current versions of Hyper-V host, only distribute UDP + packets based on the IP source and destination address. + The port number is not used as part of the hash value for UDP. + Fragmented IP packets are not distributed between queues; + all fragmented packets arrive on the first channel. + + Generic Receive Offload, aka GRO + -------------------------------- + The driver supports GRO and it is enabled by default. GRO coalesces + like packets and significantly reduces CPU usage under heavy Rx + load. + + SR-IOV support + -------------- + Hyper-V supports SR-IOV as a hardware acceleration option. If SR-IOV + is enabled in both the vSwitch and the guest configuration, then the + Virtual Function (VF) device is passed to the guest as a PCI + device. In this case, both a synthetic (netvsc) and VF device are + visible in the guest OS and both NIC's have the same MAC address. + + The VF is enslaved by netvsc device. The netvsc driver will transparently + switch the data path to the VF when it is available and up. + Network state (addresses, firewall, etc) should be applied only to the + netvsc device; the slave device should not be accessed directly in + most cases. The exceptions are if some special queue discipline or + flow direction is desired, these should be applied directly to the + VF slave device. + + Receive Buffer + -------------- + Packets are received into a receive area which is created when device + is probed. The receive area is broken into MTU sized chunks and each may + contain one or more packets. The number of receive sections may be changed + via ethtool Rx ring parameters. + + There is a similar send buffer which is used to aggregate packets for sending. + The send area is broken into chunks of 6144 bytes, each of section may + contain one or more packets. The send buffer is an optimization, the driver + will use slower method to handle very large packets or if the send buffer + area is exhausted. diff --git a/MAINTAINERS b/MAINTAINERS index 297e610c9163..d30c17df1deb 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -6294,6 +6294,7 @@ M: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> M: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx> L: devel@xxxxxxxxxxxxxxxxxxxxxx S: Maintained +F: Documentation/networking/netvsc.txt F: arch/x86/include/asm/mshyperv.h F: arch/x86/include/uapi/asm/hyperv.h F: arch/x86/kernel/cpu/mshyperv.c -- 2.11.0 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
