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From: Paolo Bonzini <pbonzini@redhat.com>
To: Eduardo Habkost <ehabkost@redhat.com>,
	Pranith Kumar <bobby.prani@gmail.com>
Cc: Richard Henderson <rth@twiddle.net>,
	"open list:All patches CC here" <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH] tcg/i386: Do not display HT warning for TCG
Date: Fri, 21 Apr 2017 11:38:30 +0200	[thread overview]
Message-ID: <8cf1d4e9-8177-3b09-5400-cb22a929e78b@redhat.com> (raw)
In-Reply-To: <20170420184210.GF25239@thinpad.lan.raisama.net>



On 20/04/2017 20:42, Eduardo Habkost wrote:
>> -smp 4,threads=4 shows 4 cores
> This means 1 socket with 1 core, 4 threads per core. But if
> vendor ID is AMD, guests will probably ignore the hyperthreading
> info and treat each thread as a separate core. That's why we have
> a warning.

I'm not sure about the "probably".  As long as the HT bit is 1 and the
number of threads is > 1 in CPUID[EAX=1].EBX[bits 23:16], I am not sure
why the OS would care about the vendor.

x86info does care (it just does not try to detect the topology for
!Intel processors), but Linux seems not to.  detect_ht is called
unconditionally.

>> I am a bit confused why smp 4 is showing only 2 cores? and why the
>> rest are showing 4 cores
> Probably because Windows XP is limited to 2 sockets.

This is correct.

Paolo

  reply	other threads:[~2017-04-21  9:38 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-19 19:54 [Qemu-devel] [RFC PATCH] tcg/i386: Do not display HT warning for TCG Pranith Kumar
2017-04-19 19:54 ` [Qemu-devel] [PATCH] " Pranith Kumar
2017-04-19 20:00   ` Pranith Kumar
2017-04-19 20:13     ` Eduardo Habkost
2017-04-19 20:16       ` Pranith Kumar
2017-04-19 20:57         ` Eduardo Habkost
2017-04-19 21:25           ` Pranith Kumar
2017-04-19 21:33             ` Eduardo Habkost
2017-04-19 22:03               ` Pranith Kumar
2017-04-20  2:26                 ` Eduardo Habkost
2017-04-20  4:14                   ` Pranith Kumar
2017-04-20 18:42                     ` Eduardo Habkost
2017-04-21  9:38                       ` Paolo Bonzini [this message]
2017-04-25 20:04                         ` Eduardo Habkost

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