Thanks for the question!

As long as caches have existed, very similar styles of side channels have been demonstrated since the late 90s. A lot of the terminology we use (flush+reload, flush+flush…) are attack techniques that have been already demonstrated on CPU caches, and these demonstrations are at least a decade old.

Flush+Reload: https://www.usenix.org/conference/usenixsecurity14/technical-sessions/presentation/yarom

Flush+Flush: https://gruss.cc/files/flushflush.pdf

Invalidate+Compare (GPU caches, 2024): https://www.usenix.org/conference/usenixsecurity24/presentation/zhang-zhenkai

My colleague, Hannes, found similar styles of attacks existed with the Linux DNS cache too: https://hannesweissteiner.com/pdfs/dmt.pdf (also published at NDSS 26!)

The one really big difference between the page-cache side channel and other side channels is the “monitor” primitive. There are methods that the OS provides which directly report the presence of a page in cache. These are syscalls like mincore (mitigated in 2019), preadv2 + rwf_nowait (unmitigated), and cachestat (mitigated in 2025).

With these syscalls, we don’t even have to rely on timing information (is page access fast -> cached; is it slow -> not cached). These syscalls really set the page-cache side channel apart because you can nondestructively figure out whether a page is in cache.

The page-cache side channel was first explored in 2019. It was explored on Linux but also on Windows by my advisor et al.: https://gruss.cc/files/pagecacheattacks.pdf

Hope this answers your question :D

Thanks for cross-posting and tagging me!