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Date:   Wed, 11 Dec 2019 08:14:05 -0800
From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     "Kang, Luwei" <luwei.kang@intel.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Chao Peng <chao.p.peng@linux.intel.com>
Subject: Re: [PATCH 1/2] KVM: VMX: Add non-canonical check on writes to RTIT
 address MSRs
Message-ID: <20191211161405.GA5722@linux.intel.com>
References: <20191210232433.4071-1-sean.j.christopherson@intel.com>
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On Tue, Dec 10, 2019 at 06:16:35PM -0800, Kang, Luwei wrote:
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index
> > 51e3b27f90ed..9aa2006dbe04 100644 --- a/arch/x86/kvm/vmx/vmx.c +++
> > b/arch/x86/kvm/vmx/vmx.c @@ -2152,6 +2152,8 @@ static int
> > vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) (index >= 2 *
> > intel_pt_validate_cap(vmx->pt_desc.caps, PT_CAP_num_address_ranges)))
> > return 1; +		if (is_noncanonical_address(data, vcpu)) +
> > return 1;
> 
> Is this for live migrate a VM with 5 level page table to the VM with 4 level
> page table?

This is orthogonal to live migration or 5-level paging.  Unless I'm missing
something, KVM simply fails to validate the incoming address.