Re: [PATCH v3] Documentation: Add section about CPU vulnerabilities for Spectre

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.