Date: Fri, 16 Sep 2011 10:12:57 -0400 From: Andrew Boyer <aboyer@averesystems.com> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-current@freebsd.org, Andriy Gapon <avg@freebsd.org> Subject: Re: Identification of HTT cores on newer (CPUID leaf 11) Intel processors Message-ID: <8C685A3B-F7E3-4F4B-87D4-56B8E9CE9FC1@averesystems.com> In-Reply-To: <201109160807.04617.jhb@freebsd.org> References: <2C3C4570-C5F9-42F5-AA81-900151590DB8@averesystems.com> <4E7106DE.40707@FreeBSD.org> <70B018CB-4658-45DD-929E-A953B299E737@averesystems.com> <201109160807.04617.jhb@freebsd.org>
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On Sep 16, 2011, at 8:07 AM, John Baldwin wrote: > I think the "right" way for an admin to disable HTT is to disable it = in the > BIOS so that it doesn't show up in the MADT. Back when we were doing = the > MPTABLE_FORCE_HTT hack having a separate tunable made sense (and it = possibly > made some limited sense if you were worried about the vulnerability on = running > machines). However, at this point I think the tunable should just go = away and > admins should configure HTT on or off in the BIOS like they would for = any > other OS. >=20 > --=20 > John Baldwin To do it this way (leave SMT enabled in the BIOS but disabled in the OS) = makes it easier to release a future upgrade to take advantage of those = cores. Once systems are distributed to customer sites it becomes very = difficult to do BIOS maintenance. -Andrew -------------------------------------------------- Andrew Boyer aboyer@averesystems.com
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