Comment by ajross

This isn't that novel though. They have the GPU set up to do cache snooping from the CPU without a protection mechanism[1] to prevent the CPU from stuffing dirty writeback entries on top of it for the GPU to see. That's not subtle or weird, and it doesn't represent a new category of attack. It's just a routine security whopper.

[1] On Intel, the IOMMU provides this. But just a cache that was aware of range-level protections (i.e. only allowed you to cache CPU-visible RAM from the CPU, etc...) would have worked.