Date: Sat, 14 May 2005 03:14:50 -0400 From: Colin Percival <cperciva@freebsd.org> To: Chris <chrcoluk@gmail.com> Cc: "Drew B. \[Security Expertise/Freelance Security research\]." <d4rkstorm@gmail.com> Subject: Re: FreeBSD Security Advisory FreeBSD-SA-05:09.htt [REVISED] Message-ID: <4285A56A.1030106@freebsd.org> In-Reply-To: <3aaaa3a050514000629cc8427@mail.gmail.com> References: <245f0df105051318564b1ffb6b@mail.gmail.com> <94145.1116037219@critter.freebsd.dk> <245f0df105051322354e8e86eb@mail.gmail.com> <3aaaa3a050514000629cc8427@mail.gmail.com>
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Chris wrote: > I am somewhat confused by applying the patch, does this disable HTT > functionality? or does a patched server close the issue and keep HTT > enabled? The patch adds a new loader tunable, machdep.hyperthreading_allowed, which is set to 0 by default. Regardless of how you try to set the machdep.hlt_cpus_mask and machdep.hlt_logical_cpus sysctls, if machdep.hyperthreading_allowed is set to zero then you will not have any process threads executing on the second hyper-thread from each core. If you're on a system where this isn't a problem (e.g., anything with no local users), you can set machdep.hyperthreading_allowed=1 in /boot/loader.conf or via the sysctl after booting, and get the benefit of hyperthreading. Colin Percival
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