not poll completed will cause the DMA ring to be full, which will
result in packet loss eventually.
-Recommended IOVA mode in async datapath
----------------------------------------
+* Recommended IOVA mode in async datapath
-When DMA devices are bound to VFIO driver, VA mode is recommended.
-For PA mode, page by page mapping may exceed IOMMU's max capability,
-better to use 1G guest hugepage.
+ When DMA devices are bound to VFIO driver, VA mode is recommended.
+ For PA mode, page by page mapping may exceed IOMMU's max capability,
+ better to use 1G guest hugepage.
-For UIO driver, any VFIO related error message can be ignored.
+ For UIO driver or kernel driver, any VFIO related error messages
+ can be ignored.