Hi Intel,
We have played a little with registers and found the correct way to enable handling. It is neccessary to clear bit 1 in PRT_L2TAGSEN.ENABLE (for STag handling). It was completely dependent on the function of register write call. We used incorrect function for pci register writing using admin queue instead of direct register writing. So now it's working as you noticed.
Thanks for your help!
Regards,
Vitaly.