Document the vnet_hdr HV parameter for KVM

Document the vnet_hdr HV parameter for KVM in the gnt-instance man page.

Signed-off-by: Stratos Psomadakis <psomas@grnet.gr>
Reviewed-by: Guido Trotter <ultrotter@google.com>

diff --git a/man/gnt-instance.rst b/man/gnt-instance.rst
index 8ce924f..d2c646d 100644 (file)
--- a/man/gnt-instance.rst
+++ b/man/gnt-instance.rst
@@ -746,6 +746,19 @@ kvm\_path
 
     Path to the userspace KVM (or qemu) program.
 
+vnet\_hdr
+    Valid for the KVM hypervisor.
+
+    This boolean option determines whether the tap devices used by the
+    KVM paravirtual nics (virtio-net) will get created with VNET_HDR
+    (IFF_VNET_HDR) support.
+
+    If set to false, it effectively disables offloading on the virio-net
+    interfaces, which prevents host kernel tainting and log flooding,
+    when dealing with broken or malicious virtio-net drivers.
+
+    It is set to ``true`` by default.
+
 The ``-O (--os-parameters)`` option allows customisation of the OS
 parameters. The actual parameter names and values depends on the OS
 being used, but the syntax is the same key=value. For example, setting