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-rw-r--r--doc/guides/sample_app_ug/vhost.rst21
1 files changed, 13 insertions, 8 deletions
diff --git a/doc/guides/sample_app_ug/vhost.rst b/doc/guides/sample_app_ug/vhost.rst
index a4bdc6a4..9112e789 100644
--- 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
@@ -175,15 +178,17 @@ Common Issues
The command above indicates how many hugepages are free to support QEMU's
allocation request.
-* vhost-user will not work with QEMU without the ``-mem-prealloc`` option
+* Failed to build DPDK in VM
- The current implementation works properly only when the guest memory is
- pre-allocated.
+ Make sure "-cpu host" QEMU option is given.
-* vhost-user will not work with a QEMU version without shared memory mapping:
+* Device start fails if NIC's max queues > the default number of 128
- Make sure ``share=on`` QEMU option is given.
+ mbuf pool size is dependent on the MAX_QUEUES configuration, if NIC's
+ max queue number is larger than 128, device start will fail due to
+ insufficient mbuf.
-* Failed to build DPDK in VM
+ Change the default number to make it work as below, just set the number
+ according to the NIC's property. ::
- Make sure "-cpu host" QEMU option is given.
+ make EXTRA_CFLAGS="-DMAX_QUEUES=320"