ethdev: deprecate port count function

[dpdk.git] / doc / guides / sample_app_ug / vhost.rst

diff --git a/doc/guides/sample_app_ug/vhost.rst b/doc/guides/sample_app_ug/vhost.rst
index da161a9a91ae93d020761fa38f9cc94f95f58d89..5e7f24c4e8bd75f940b176c1aba655c3825d78d2 100644 (file)
--- a/doc/guides/sample_app_ug/vhost.rst
+++ b/doc/guides/sample_app_ug/vhost.rst
@@ -147,7 +147,10 @@ retries on an RX burst, it takes effect only when rx retry is enabled. The
 default value is 15.
 
 **--dequeue-zero-copy**
-Dequeue zero copy will be enabled when this option is given.
+Dequeue zero copy will be enabled when this option is given. it is worth to
+note that if NIC is binded to driver with iommu enabled, dequeue zero copy
+cannot work at VM2NIC mode (vm2vm=0) due to currently we don't setup iommu
+dma mapping for guest memory.
 
 **--vlan-strip 0|1**
 VLAN strip option is removed, because different NICs have different behaviors