From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:57606)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1XbcQe-0001oh-I8
	for qemu-devel@nongnu.org; Tue, 07 Oct 2014 17:36:26 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1XbcQX-0008Ov-Iz
	for qemu-devel@nongnu.org; Tue, 07 Oct 2014 17:36:20 -0400
Received: from mx1.redhat.com ([209.132.183.28]:25214)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1XbcQX-0008Of-BW
	for qemu-devel@nongnu.org; Tue, 07 Oct 2014 17:36:13 -0400
Message-ID: <54345CC8.8050806@redhat.com>
Date: Tue, 07 Oct 2014 23:36:08 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
MIME-Version: 1.0
References: <1412711059-12524-1-git-send-email-wei@redhat.com>
	<543453D9.8020706@redhat.com> <54345843.8070703@redhat.com>
In-Reply-To: <54345843.8070703@redhat.com>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH 1/1] target-i386: prevent users from
 setting threads>1 for AMD CPUs
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Wei Huang <wei@redhat.com>, afaerber@suse.de
Cc: qemu-devel@nongnu.org

Il 07/10/2014 23:16, Wei Huang ha scritto:
> It isn't a bug IMO. I tested various combinations; and current QEMU
> handles it very well. It converts threads=n to proper
> CPUID_0000_0001_EBX[LogicalProcCount] and CPUID_8000_0008_ECX[NC]
> accordingly for AMD.

So if it ain't broken, don't fix it. :)

>> I am worried that the default CPU is an AMD one when KVM is disabled,
>> and thus "qemu-system-x86_64 -smp threads=2" will likely be broken.
> 
> "-smp threads=2" will be rejected by the patch.

Yeah, I am afraid that is an incompatible change, and one more reason
not to do this.  AMD not selling hyperthreaded processors does not mean
that they could not be represented properly with the CPUID leaves that
AMD processors support.

Paolo

> Unless the meaning of
> threads is not limited to threads-per-core, shouldn't end users use
> "-smp 2" in this case or something like "-smp 2,cores=2,sockets=1"?