linux-kernel - Re: [PATCH v4 3/3] KVM: nVMX: Emulate EPTP switching for the L1 hypervisor

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Date:   Tue, 11 Jul 2017 14:35:00 -0400
From:   Bandan Das <bsd@...hat.com>
To:     Jim Mattson <jmattson@...gle.com>
Cc:     David Hildenbrand <david@...hat.com>,
        kvm list <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/3] KVM: nVMX: Emulate EPTP switching for the L1 hypervisor

Jim Mattson <jmattson@...gle.com> writes:
...
>>> I can find the definition for an vmexit in case of index >=
>>> VMFUNC_EPTP_ENTRIES, but not for !vmcs12->eptp_list_address in the SDM.
>>>
>>> Can you give me a hint?
>>
>> I don't think there is. Since, we are basically emulating eptp switching
>> for L2, this is a good check to have.
>
> There is nothing wrong with a hypervisor using physical page 0 for
> whatever purpose it likes, including an EPTP list.

Right, but of all the things, a l1 hypervisor wanting page 0 for a eptp list
address most likely means it forgot to initialize it. Whatever damage it does will
still end up with vmfunc vmexit anyway.

Bandan