Date: Sun, 13 Nov 2005 15:39:19 -0800 (PST) From: Doug White <dwhite@gumbysoft.com> To: kama <kama@pvp.se> Cc: freebsd-stable@freebsd.org Subject: Re: Hyperthreading issues. Message-ID: <20051113153531.B7337@carver.gumbysoft.com> In-Reply-To: <20051111204659.F8860@ns1.as.pvp.se> References: <20051111204659.F8860@ns1.as.pvp.se>
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On Fri, 11 Nov 2005, kama wrote: > Just upgraded from 5.4 to 6.0 and hyperthreading stoped working. > Everything looks ok, but it doesn't use two of the logical CPU's. This is disabled by default due to a information-leak vulnerability across the hyperthreaded cores. The details from the release notes: Because of an information disclosure vulnerability on processors using Hyper-Threading Technology (HTT), the machdep.hyperthreading_allowed sysctl variable has been added. It defaults to 1 (HTT enabled) on FreeBSD CURRENT, and 0 (HTT disabled) on the 4-STABLE and 5-STABLE development branches and supported security fix branches. More information can be found in security advisory FreeBSD-SA-05:09.htt. [MERGED] If you don't care about this, add machdep.hyperthreading_allowed="1" to /boot/loader.conf and reboot. > One other thing is when I try to switch off hyperthreading in BIOS, it > will hang at bootup when it are settling the scsi drives. After awhile it > will give me scsi timeouts. This only happens when I have two cpu enabled > and hyperthreading off. If I disable one cpu w ht off it will boot wo > problems, or two cpus w ht. But booting with ht + two cpu's gives me the > other problem. Sounds like the BIOS is not rerouting the interrupts correctly. Check for a BIOS update. -- Doug White | FreeBSD: The Power to Serve dwhite@gumbysoft.com | www.FreeBSD.org
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