linux-kernel - Re: [PATCH 4/4] x86: properly handle kvm emulation of hyperv

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Message-ID: <51EF7A2A.6040003@redhat.com>
Date:	Wed, 24 Jul 2013 14:54:34 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	KY Srinivasan <kys@...rosoft.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"gleb@...hat.com" <gleb@...hat.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] x86: properly handle kvm emulation of hyperv

On 07/24/2013 12:48 PM, H. Peter Anvin wrote:
> On 07/23/2013 09:37 PM, Jason Wang wrote:
>> On 07/23/2013 10:48 PM, H. Peter Anvin wrote:
>>> On 07/23/2013 06:55 AM, KY Srinivasan wrote:
>>>> This strategy of hypervisor detection based on some detection order IMHO is not
>>>> a robust detection strategy. The current scheme works since the only hypervisor emulated
>>>> (by other hypervisors happens to be Hyper-V). What if this were to change.
>>>>
>>> One strategy would be to pick the *last* one in the CPUID list, since
>>> the ones before it are logically the one(s) being emulated...
>>>
>>> 	-hpa
>>>
>> How about simply does a reverse loop from 0x40010000 to 0x40010000?
>>
> Not all systems like being poked too far into hyperspace.  Just remember
> the last match and walk the list.
>
> 	-hpa
>

Ok, but it raises a question - how to know it was the 'last' match
without knowing all signatures of other hyper-visor?

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