On Wed 2018-02-14 22:44:44, joe.korty@xxxxxxxxxxxxxxxxx wrote: > On Wed, Feb 14, 2018 at 11:43:42AM +0100, Pavel Machek wrote: > > We have just found out that majority of 64-bit machines are broken in > > rather fundamental ways (Spectre) and Intel does not even look > > interested in fixing that (because it would make them look bad on > > benchmarks). > > > > Even when the Spectre bug is mitigated... this looks like can of worms > > that can not be closed. > > > > OTOH -- we do know that there are non-broken machines out there, > > unfortunately they are mostly 32-bit :-). Removing support for > > majority of working machines may not be good idea... > > > > [And I really hope future CPUs get at least option to treat cache miss > > as a side-effect -- thus disalowed during speculation -- and probably > > option to turn off speculation altogether. AFAICT, it should "only" > > result in 50% slowdown -- or that was result in some riscv > > presentation.] > > Or, future CPU designs introduce shadow caches and shadow > TLBs which only speculation loads and sees and which > become real only if and whend the resultant speculative > calculations become real. Yes, that could help. But there's still sidechannel in the RAM: it has row buffer or something like that. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
Attachment:
signature.asc
Description: Digital signature
