Date: Mon, 14 Nov 2005 14:24:03 +0100 (CET) From: kama <kama@pvp.se> To: Doug White <dwhite@gumbysoft.com> Cc: freebsd-stable@freebsd.org Subject: Re: Hyperthreading issues. Message-ID: <20051114142001.W20948@ns1.as.pvp.se> In-Reply-To: <20051113153531.B7337@carver.gumbysoft.com> References: <20051111204659.F8860@ns1.as.pvp.se> <20051113153531.B7337@carver.gumbysoft.com>
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On Sun, 13 Nov 2005, Doug White wrote: > 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. If you had read the mail you'll see further down that its indeed set. After a while it seems to use cpu2&3 but more rarely than 1&0, maybe its ULE that makes it work that way. > > > 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. > I'll see if there is a new BIOS update. /Bjorn
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