-> Download the Kernel.elf file
-> Save it to the folder which has the fast boot binaries (fastboot.exe file).
-> Turnoff the phone to the fast boot mode.
-> Connect the phone and the power button down and the volume key up.
-> Enter into the fast boot mode.
-> Open cmd in pc and type fastboot flash boot kernel.elf
-> Restart your device.
for the above procedure to work you need to unlock your bootloader and for that visit talk.sony.com and check wether unlocking bootloader supports your device
I've got a sola n unlocked and rooted my device