Deutsch English Français Italiano |
<2024Jul26.183607@mips.complang.tuwien.ac.at> View for Bookmarking (what is this?) Look up another Usenet article |
Path: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: anton@mips.complang.tuwien.ac.at (Anton Ertl) Newsgroups: comp.arch Subject: Re: Chipsandcheese article on the CDC6600 Date: Fri, 26 Jul 2024 16:36:07 GMT Organization: Institut fuer Computersprachen, Technische Universitaet Wien Lines: 28 Message-ID: <2024Jul26.183607@mips.complang.tuwien.ac.at> References: <v7fss8$3f712$1@dont-email.me> <v7k7ok$a7tn$5@dont-email.me> <lg6gtgFlcf1U1@mid.individual.net> <20240722130827.00004fea@yahoo.com> <2024Jul22.145235@mips.complang.tuwien.ac.at> <CCunO.76231$oGQf.17922@fx10.iad> <v7n2pg$t929$7@dont-email.me> <p6OnO.164803$SLqf.57968@fx15.iad> <v7ph70$1dsq8$6@dont-email.me> <Ge7oO.153178$sE%9.112738@fx14.iad> <v7s3n9$1uqcm$5@dont-email.me> <2024Jul25.125916@mips.complang.tuwien.ac.at> <cfdc79a2dcf70e18792093605f27ef67@www.novabbs.org> Injection-Date: Fri, 26 Jul 2024 18:54:17 +0200 (CEST) Injection-Info: dont-email.me; posting-host="db2ff68befcdcab7a74f905c9b0b3b66"; logging-data="3066015"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX194IsqdpwHVpzUR2hPwLaUt" Cancel-Lock: sha1:IcrdnlEJBfB59imAxhEpKtzyo7c= X-newsreader: xrn 10.11 Bytes: 2582 mitchalsup@aol.com (MitchAlsup1) writes: >On Thu, 25 Jul 2024 10:59:16 +0000, Anton Ertl wrote: >> Now somebody will point out that sharing makes it possible for an >> attacker to train branch predictors in one process to attack a >> different process through Spectre and friends. While preventing >> sharing would close that, it does not close training the predictors in >> the same thread. > >Not allowing a dependent AGEN to happen when the first AGEN takes >a fault ALSO prevents SPectré like attacks Spectre does not need a fault. You are probably thinking of Meltdown. That, at least has been fixed by Intel (and hopefully also ARM) in its original variant pretty soon, although other variants have been discovered since then (IIRC including some where the fault has nothing to do with addresses). >Then not modifying >any cache prior to instruction retirement cements the door closed. Not changing microarchitectural state (not just caches) through misspeculation (invisible speculation) is a proper fix for Spectre, and looks like the best fix to me. - anton -- 'Anyone trying for "industrial quality" ISA should avoid undefined behavior.' Mitch Alsup, <c17fcd89-f024-40e7-a594-88a85ac10d20o@googlegroups.com>