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Re: [Qemu-devel] [PATCH] tcg/i386: Do not display HT warning for TCG

From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH] tcg/i386: Do not display HT warning for TCG
Date: Fri, 21 Apr 2017 11:38:30 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0

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

>> 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.


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