linux-kernel - Re: [PATCH 4/4] nvmx: check for shadow vmcs check on entry

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Date:	Fri, 22 Jul 2016 11:51:44 -0400
From:	Bandan Das <bsd@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	kvm@...r.kernel.org, rkrcmar@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] nvmx: check for shadow vmcs check on entry

Paolo Bonzini <pbonzini@...hat.com> writes:

>> Paolo Bonzini <pbonzini@...hat.com> writes:
>> 
>> > On 21/07/2016 00:25, Bandan Das wrote:
>> >> vmentry should check whether the vmcs provided by
>> >> the guest hypervisor is a shadow vmcs and fail.
>> >
>> > How can this happen, since vmptrld checks the revision_id as you said
>> > below?
>> 
>> This is more of a change that adheres to the spec
>> (26.1 Basic VM-Entry Checks); the failure path
>> is slightly different compared to vmptrld though.
>> It's small and harmless but I am ok if you prefer dropping it.
>
> Do you mean that this could happen if the VMCS is modified by L1
> after VMPTRLD?  That makes sense, but with David Matlack's change

Yeah that's the only way I can see it happen. If there's a separate path
that takes care of this, should I drop this one ?

> to cache the VMCS it wouldn't be possible to trigger it anymore.
>
> Paolo
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