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

[Jon Masters]

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.

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