Date: Sat, 21 May 2005 17:49:20 -0700 From: Colin Percival <cperciva@freebsd.org> To: Marcel Moolenaar <marcel@xcllnt.net> Cc: freebsd-arch@freebsd.org Subject: Re: Scheduler fixes for hyperthreading Message-ID: <428FD710.4060200@freebsd.org> In-Reply-To: <aef05e1ae6104223181ad3cf03e11390@xcllnt.net> References: <428FC00B.3080909@freebsd.org> <aef05e1ae6104223181ad3cf03e11390@xcllnt.net>
next in thread | previous in thread | raw e-mail | index | archive | help
Marcel Moolenaar wrote: > On May 21, 2005, at 4:11 PM, Colin Percival wrote: >> The following must be done before hyperthreading is re-enabled: >> [snip] > > Maybe it's a better idea to describe the problem in much more > detail, rather than dictate what you want someone else to do? > A pointer to where the problem is described/discussed would > do. The problem is described in my paper "Cache missing for fun and profit": http://www.daemonology.net/papers/htt.pdf Put simply, threads which share a processor core can monitor each others' memory access patterns, so we need to ensure that such co-scheduling never happens between threads which have different privileges. The reason I cut through to explaining what needed to be done is that I discussed this at length with several people from the FreeBSD security team before and during BSDCan; but these discussions were obviously not public, so I can't give a reference to them. Colin Percival
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?428FD710.4060200>