Here's the crux of the memory issue from one of the link in the article:
DDR memory is laid out in an array of rows and columns, which are assigned in large blocks to various applications and operating system resources. To protect the integrity and security of the entire system, each large chunk of memory is contained in a "sandbox" that can be accessed only by a given app or OS process. Bit flipping works when a hacker-developed app or process accesses two carefully selected rows of memory hundreds of thousands of times in a tiny fraction of a second. By hammering the two "aggressor" memory regions, the exploit can reverse one or more bits in a third "victim" location. In other words, selected zeros in the victim region will turn into ones or vice versa.
Rowhammer itself has been around a while, and is only 50% of this attack that has been posted.
The other bit is the newer idea (well, old idea, newer actual implementation); memory deduplication by your hypervisor leads to a very minor timing fingerprint when you write to a page of memory that had previously been deduplicated IE the same physical page was shared amongst multiple VM's because it was identical.. until you wrote to it and the OS/hardware had to then Copy-on-Write it out to your own dedicated copy; that has a higher latency than a memory page that is already available directly for writing to you.
DDR memory is laid out in an array of rows and columns, which are assigned in large blocks to various applications and operating system resources. To protect the integrity and security of the entire system, each large chunk of memory is contained in a "sandbox" that can be accessed only by a given app or OS process. Bit flipping works when a hacker-developed app or process accesses two carefully selected rows of memory hundreds of thousands of times in a tiny fraction of a second. By hammering the two "aggressor" memory regions, the exploit can reverse one or more bits in a third "victim" location. In other words, selected zeros in the victim region will turn into ones or vice versa.