On 1/31/19 1:08 PM, Jiri Kosina wrote: > On Thu, 31 Jan 2019, Daniel Gruss wrote: > >> If I understood it correctly, this patch just removes the advantages of >> preadv2 over mmmap+access for the attacker. > > Which is the desired effect. We are not trying to solve the timing aspect, > as I don't think there is a reasonable way to do it, is there? There are two building blocks to cache attacks, bringing the cache into a state, and observing a state change, you can mitigate them by breaking either of these building blocks. For most attacks the attacker would be interested in observing *when* a specific victim page is loaded into the page cache rather than observing whether it is in the page cache right now (it could be there for ages if the system was not under memory pressure). So, one could try to prevent interference in the page cache between attacker and victim -> working set algorithms do that to some extent. Simpler idea (with more side effects) would be limiting the maximum share of the page cache per user (or per process, depending on the threat model)... Cheers, Daniel
