On Thu 23-08-18 08:46:48, Andi Kleen wrote: > On Thu, Aug 23, 2018 at 04:28:12PM +0200, Vlastimil Babka wrote: > > Two users have reported [1] that they have an "extremely unlikely" system > > with more than MAX_PA/2 memory and L1TF mitigation is not effective. Let's > > make the warning more helpful by suggesting the proper mem=X kernel boot param, > > a rough calculation of how much RAM can be lost (not precise if there's holes > > between MAX_PA/2 and max_pfn in the e820 map) and a link to the L1TF document > > to help decide if the mitigation is worth the unusable RAM. > > I'm not sure anyone would really do that. After all you probably prefer > your memory. And if it's really a non ECC client part they are are > already used to to live very dangerously because their undetected RAM bit error > rate will be significant. L1TF is probably one of your smaller problems > in this case... There are people who care about L1TF mitigations. I am not going to question their motivation. In any case a hint how to make the mitigation active again sounds more useful than something that sounds as scary as "you are vulnerable". -- Michal Hocko SUSE Labs
