From mboxrd@z Thu Jan  1 00:00:00 1970
From: Bandan Das <bsd@redhat.com>
Subject: Re: [PATCH v4 3/3] KVM: nVMX: Emulate EPTP switching for the L1 hypervisor
Date: Tue, 11 Jul 2017 14:35:00 -0400
Message-ID: <jpga84ayg8b.fsf@linux.bootlegged.copy>
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        <20170710204936.4001-4-bsd@redhat.com>
        <2d50ebc4-9328-ce08-b55b-6a331ee13cc3@redhat.com>
        <jpgy3ruam9i.fsf@linux.bootlegged.copy>
        <CALMp9eQyWQyyyP=K1+HieiQJHvBFzMEFGufOz6BFgb-mmdQm=Q@mail.gmail.com>
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Cc: David Hildenbrand <david@redhat.com>,
        kvm list <kvm@vger.kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>
To: Jim Mattson <jmattson@google.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <CALMp9eQyWQyyyP=K1+HieiQJHvBFzMEFGufOz6BFgb-mmdQm=Q@mail.gmail.com>
        (Jim Mattson's message of "Tue, 11 Jul 2017 11:22:37 -0700")
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

Jim Mattson <jmattson@google.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