OK, its simple and almost anyone can do it. Just follow the steps and you will get a working root access
1. Flash the JellyBean build
2. Download and put this flashable zip (Superuser) in the root of the SD Card Download here
3. Flash any ICS kernel, I recommend ThP because there is a Power Off option and its easier Link Here (And yeah, if you are asking yourself if the ICS kernel will work on JB, it wont. The phone will stuck at bootloop.) or Nemesis Kernel
4. Flash the zip and power off the device from recovery
5. Flash the JellyBean kernel. It can be found here LINK
6. Power on the device and Enjoy !
I am working on TWRP for the new JellyBean kernel, stay tuned !
Flash ThP Kernel HERE. It has autoroot function
For Locked Bootloader
There are some regions where OTA update is available. Some of you might try the following:
- root any ICS ROM
- install ОТА Root Keeper
- update via OTA
If you have country problems in which the update isn't available yet, try changing the SI codes. The method can be found here.
Featured on Xperia Blog:
Root workaround available for Xperia P Jelly Bean firmware