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To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Lin Ming <ming.m.lin@intel.com>,
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Subject: Re: [PATCH 4/7] perf: Check if HT is supported and enabled
In-Reply-To: Your message of "Tue, 04 Jan 2011 12:10:19 +0100."
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From: Valdis.Kletnieks@vt.edu
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On Tue, 04 Jan 2011 12:10:19 +0100, Peter Zijlstra said:

> X86_FEATURE_HT tells us the CPU supports telling us about HT,
> smp_num_siblings > 1 tells us the CPU is capable of HT.

A subtle but important distinction. Several laptops ago, I had a P4-M chip that
had FEATURE_HT, but num_siblings == 1.  ISTR trying to boot an SMP kernel on it
and it dying gloriously trying to bring up the non-existent other sibling.


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