[Cryptography] Speculation considered harmful?

[Howard Chu]

Henry Baker wrote:

> So-called "two phase commit protocols" attempt to gather all the information and resources necessary to *complete* a transaction prior to "committing" the transaction.  If the transaction can't be completed, than it must need to be "rolled back" -- a process of *undoing* any actions that were done during the gathering phase.
> 
> There's only one slight problem: you can't unring a bell: you can't "unlearn"/"forget" a bit that you learned during the gathering phase.  Or more precisely, you can't force a party to the transaction to forget such bits.
> 
> I don't have a clean solution to this "forgetting" problem, and I doubt that anyone else does, either.

Eh. In the context of Spectre, the CPU knows which cachelines it loaded in a 
speculative fetch. It should simply mark them invalid when unrolling the 
speculation.

-- 
   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/