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Subject: Re: [PATCH] KVM: nVMX: VMX instructions: fix segment checks when L1
 is in long mode.
To: Quentin Casasnovas <quentin.casasnovas@oracle.com>, x86 <x86@kernel.org>,
        kvm <kvm@vger.kernel.org>, lkml <linux-kernel@vger.kernel.org>
References: <1466240465-19318-1-git-send-email-quentin.casasnovas@oracle.com>
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        linux-stable <stable@vger.kernel.org>
From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Thu, 23 Jun 2016 18:03:01 +0200
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On 18/06/2016 11:01, Quentin Casasnovas wrote:
> Cross-checking the KVM/VMX VMREAD emulation code with the Intel Software
> Developper Manual Volume 3C - "VMREAD - Read Field from Virtual-Machine
> Control Structure", I found that we're enforcing that the destination
> operand is NOT located in a read-only data segment or any code segment when
> the L1 is in long mode - BUT that check should only happen when it is in
> protected mode.
> 
> Shuffling the code a bit to make our emulation follow the specification
> allows me to boot a Xen dom0 in a nested KVM and start HVM L2 guests
> without problems.

That's great, and I'm applying the patch, but it's also pretty weird. :)
 Do you have a pointer to Xen source code that does a VMREAD into a
read-only data segment or a code segment?

Thanks,

Paolo