Thanks for visiting the forum and using the Intel X520 adapter.
We do not have HBA type offloads in our devices - they do not scale well with increasing processor speeds. What we do have are intelligent offloads, such as checksum calculation in the CPU, which do scale.
To use iSCSI with the X520 you need to use the software initiator.
If you go digging into VMware's BKM documents, you will find that they tell you to turn off all hardware offloads on HBA's. This is because they found that those offloads cannot keep pace with the data under stress on newer generation processors and errors occur.
Hope this helps.