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Date: Thu, 05 Jun 2014 18:26:41 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [RFC 0/2] GET_EMULATED_CPUID support with
	"allow-emulation" option
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To: Alexander Graf <agraf@suse.de>, Eduardo Habkost <ehabkost@redhat.com>, qemu-devel@nongnu.org
Cc: Michael Mueller <mimu@linux.vnet.ibm.com>, kvm@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>, Christian Borntraeger <borntraeger@de.ibm.com>, "Gabriel L. Somlo" <gsomlo@gmail.com>, Borislav Petkov <bp@alien8.de>, "Jason J. Herne" <jjherne@linux.vnet.ibm.com>, =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= <afaerber@suse.de>

Il 05/06/2014 18:24, Alexander Graf ha scritto:
>
> On 05.06.14 18:12, Eduardo Habkost wrote:
>> This implements GET_SUPPORTED_CPUID support using an explicit option
>> for it:
>> "allow-emulation". We don't want any emulated feature to be enabled by
>> accident,
>> so they will be enabled only if the user explicitly wants to allow them.
>
> So is this an all-or-nothing approach? I would really prefer to override
> individual bits.

You can still disable them with "cpu foo,-movbe,allow-emulation".

> Also, I don't think the line "emulated" is the right one to draw. We
> "emulate" SVM or VMX too, but still enable them by default as soon as we
> think they're ready enough.

Well, I disagreed with the whole KVM_GET_EMULATED_CPUID concept for 
MOVBE too for example.  It seemed overengineered to me, sooner or later 
we might graduate MOVBE out of KVM_GET_EMULATED_CPUID as well.

However, for MONITOR/MWAIT it makes some sense.

Paolo