Messages in this thread | | | From | KY Srinivasan <> | Subject | RE: [PATCH 4/4] x86: properly handle kvm emulation of hyperv | Date | Tue, 23 Jul 2013 17:45:04 +0000 |
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> -----Original Message----- > From: H. Peter Anvin [mailto:hpa@zytor.com] > Sent: Tuesday, July 23, 2013 10:48 AM > To: KY Srinivasan > Cc: Jason Wang; tglx@linutronix.de; mingo@redhat.com; x86@kernel.org; > gleb@redhat.com; pbonzini@redhat.com; kvm@vger.kernel.org; linux- > kernel@vger.kernel.org > Subject: Re: [PATCH 4/4] x86: properly handle kvm emulation of hyperv > > 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...
Is it always possible to guarantee this ordering. As a hypothetical, what if hypervisor A emulates Hypervisor B and Hypervisor B emulates Hypervisor A. In this case we cannot have any "order" based detection that can yield "correct" detection. I define "correctness" as follows:
If a guest can run on both the hypervisors, the guest should detect the true native Hypervisor.
Regards,
K. Y
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