net: documentation: build a directory structure for drivers

Documentation/networking/ is full of cryptically named files with
driver documentation.  This makes finding interesting information
at a glance really hard.  Move all those files into a directory
called device_drivers (since not all drivers are for device) and
fix up references.

RFC v0.1 -> RFC v1:
 - also add .txt suffix to the files which are missing it (Quentin)

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: David Ahern <dsahern@gmail.com>
Acked-by: Henrik Austad <henrik@austad.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 84 insertions, 0 deletions

diff --git a/Documentation/networking/device_drivers/microsoft/netvsc.txt b/Documentation/networking/device_drivers/microsoft/netvsc.txt
new file mode 100644
index 000000000000..3bfa635bbbd5
--- /dev/null
+++ b/Documentation/networking/device_drivers/microsoft/netvsc.txt
@@ -0,0 +1,84 @@
+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 & UDP, packets can
+  be distributed among available queues based on IP address and port
+  number.
+
+  For TCP & UDP, we can switch hash level between L3 and L4 by ethtool
+  command. TCP/UDP over IPv4 and v6 can be set differently. The default
+  hash level is L4. We currently only allow switching TX hash level
+  from within the guests.
+
+  On Azure, fragmented UDP packets have high loss rate with L4
+  hashing. Using L3 hashing is recommended in this case.
+
+  For example, for UDP over IPv4 on eth0:
+  To include UDP port numbers in hashing:
+        ethtool -N eth0 rx-flow-hash udp4 sdfn
+  To exclude UDP port numbers in hashing:
+        ethtool -N eth0 rx-flow-hash udp4 sd
+  To show UDP hash level:
+        ethtool -n eth0 rx-flow-hash udp4
+
+  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.
+
+  Large Receive Offload (LRO), or Receive Side Coalescing (RSC)
+  -------------------------------------------------------------
+  The driver supports LRO/RSC in the vSwitch feature. It reduces the per packet
+  processing overhead by coalescing multiple TCP segments when possible. The
+  feature is enabled by default on VMs running on Windows Server 2019 and
+  later. It may be changed by ethtool command:
+	ethtool -K eth0 lro on
+	ethtool -K eth0 lro off
+
+  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.