Date: Mon, 23 May 2005 03:54:26 +0200 From: Anton Bobrov <Anton.Bobrov@Sun.COM> To: Colin Percival <cperciva@freebsd.org> Cc: freebsd-arch@freebsd.org Subject: Re: Scheduler fixes for hyperthreading Message-ID: <429137D2.10801@sun.com> In-Reply-To: <428FC00B.3080909@freebsd.org> References: <428FC00B.3080909@freebsd.org>
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or perhaps processor sets + processor bindings + tweakable config/api system to allow users to do what they like could address that, no? i know thats alot of work however what you suggest in point 1 + point 2 aint a piece of cake either so as long as somebody goes with the complication maybe its a good idea to make a flexible system that will address other problems and benefits as well? just a thought... Colin Percival wrote: > As you are probably all aware by now, HyperThreading has been > disabled on the stable and security branches due to a problem > with information leakage between threads which are scheduled > simultaneously on the two processor cores. Clearly, some people > (and at least one large company) are unhappy about us having > hyperthreading disbaled, so the security team would like to see > hyperthreading re-enabled by default as soon as we believe that > this can be done safely. > > The following must be done before hyperthreading is re-enabled: > > 1. The scheduler must be taught to not run threads on the same > processor core unless they p_candebug() each other. For reasons > of performance and locking, this is probably best accomplished by > only allowing threads to share a processor core if they belong > to the same process. > 2. When a thread is in the kernel, there must be a mechanism for > it to IPI its siblings and put them to sleep, and then wake them > up later. This would be used any time when a thread in the kernel > is about to handle sensitive data in a non-oblivious manner; IPsec > is a good example of where this would be necessary. > > Does anyone want to step forward to work on this? > > Colin Percival > _______________________________________________ > freebsd-arch@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-arch > To unsubscribe, send any mail to "freebsd-arch-unsubscribe@freebsd.org"
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