On 6/17/19 4:22 PM, Jon Masters wrote: >> + For kernel code that has been identified where data pointers could >> + potentially be influenced for Spectre attacks, new "nospec" accessor >> + macros are used to prevent speculative loading of data. > > Maybe explain that nospec (speculative clamping) relies on the absence > of value prediction in the masking (in current hardware). It may NOT > always be a safe approach in future hardware, where Spectre-v1 attacks > are likely to persist but hardware may speculate about the mask value. Something like the Arm CSDB barrier would seem to be potentially useful for $FUTURE_X86 as a fence with lighter-weight semantics than an *fence. Jon. -- Computer Architect | Sent with my Fedora powered laptop
