From: Paolo Bonzini <pbonzini@redhat.com>
To: Eduardo Habkost <ehabkost@redhat.com>
Cc: Jidong Xiao <jidong.xiao@gmail.com>,
qemu-devel@nongnu.org, KVM <kvm@vger.kernel.org>
Subject: Re: [Qemu-devel] [PATCH] Qemu: Fix eax for cpuid leaf 0x40000000
Date: Wed, 13 Aug 2014 14:18:51 +0200 [thread overview]
Message-ID: <53EB57AB.60801@redhat.com> (raw)
In-Reply-To: <20140812192952.GK3011@thinpad.lan.raisama.net>
Il 12/08/2014 21:29, Eduardo Habkost ha scritto:
> On Tue, Aug 12, 2014 at 09:12:00PM +0200, Paolo Bonzini wrote:
>> Il 12/08/2014 20:55, Eduardo Habkost ha scritto:
>>> This makes the CPUID data change under the guest's feet during
>>> live-migration.
>>>
>>> Adding compat code to ensure older machine-types keep the old behavior
>>> is necessary, but in this specific case it is mostly harmless because
>>> 0x0 is documented as being equivalent to 0x40000001.
>>>
>>> (But I don't know how guests are supposed to behave when they see
>>> CPUID[KVM_CPUID_SIGNATURE_NEXT].EAX==0.)
>>
>> The only obvious thing to do would be to treat it as 0x40000101.
>
> I just want to be sure the guests really do that. If we know guests
> won't do anything different with the CPUID change, I won't mind having
> no compat code for this.
>
Considering that only two leaves are defined for KVM, and both are
mandatory I don't think current guests have any reason to look at
CPUID[KVM_CPUID_SIGNATURE | kvm_base].EAX at all.
Paolo
prev parent reply other threads:[~2014-08-13 12:20 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-04 1:10 [PATCH] Qemu: Fix eax for cpuid leaf 0x40000000 Jidong Xiao
2014-06-04 7:09 ` Paolo Bonzini
2014-06-04 7:17 ` Jidong Xiao
2014-06-04 19:08 ` [Qemu-devel] " Bandan Das
2014-06-04 19:47 ` Jidong Xiao
2014-06-04 21:26 ` [Qemu-devel] " Bandan Das
2014-08-12 18:55 ` Eduardo Habkost
2014-08-12 19:12 ` Paolo Bonzini
2014-08-12 19:29 ` Eduardo Habkost
2014-08-13 12:18 ` Paolo Bonzini [this message]
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