AES CTR is used for encryption. Now, 8-bit bytes are used so that does limit what one can do, but if in addition a unique 8-bit involution was used to encrypt the data in each memory page, in order to successfully rowhammer bits, it would require obtaining the full codebook for the target data.

I realize this solution is so simple it may have simply not occurred to anyone of you. But now I've proposed it, so maybe the cybersecurity everyone needs gets closer to being realized.