linux-kernel - Re: [PATCH v2 1/3] KVM: nVMX: Always call sync_vmcs02_to_vmcs12

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Date:   Thu, 21 Jan 2021 15:59:42 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Cc:     kvm@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        x86@...nel.org, Borislav Petkov <bp@...en8.de>,
        Ingo Molnar <mingo@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Wanpeng Li <wanpengli@...cent.com>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH v2 1/3] KVM: nVMX: Always call sync_vmcs02_to_vmcs12_rare
 on migration

On 15/01/21 00:58, Sean Christopherson wrote:
> Reviewed-by: Sean Christopherson<seanjc@...gle.com>  

New commit message:

KVM: nVMX: Sync unsync'd vmcs02 state to vmcs12 on migration

Even when we are outside the nested guest, some vmcs02 fields
may not be in sync vs vmcs12.  This is intentional, even across
nested VM-exit, because the sync can be delayed until the nested
hypervisor performs a VMCLEAR or a VMREAD/VMWRITE that affects those
rarely accessed fields.

However, during KVM_GET_NESTED_STATE, the vmcs12 has to be up to date to
be able to restore it.  To fix that, call copy_vmcs02_to_vmcs12_rare()
before the vmcs12 contents are copied to userspace.

Paolo