linux-kernel - Re: [PATCH 01/43] KVM: nVMX: Set LDTR to its architecturally defined value on nested VM-Exit

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Message-ID: <CAAeT=FzRbCLT1AKE4QYbG6LwUhgtRfgjRDPVqsu0Y8QU+USHeA@mail.gmail.com>
Date:   Tue, 18 May 2021 22:30:18 -0700
From:   Reiji Watanabe <reijiw@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/43] KVM: nVMX: Set LDTR to its architecturally defined
 value on nested VM-Exit

On Fri, Apr 23, 2021 at 5:47 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> Set L1's LDTR on VM-Exit per the Intel SDM:
>
>   The host-state area does not contain a selector field for LDTR. LDTR is
>   established as follows on all VM exits: the selector is cleared to
>   0000H, the segment is marked unusable and is otherwise undefined
>   (although the base address is always canonical).
>
> This is likely a benign bug since the LDTR is unusable, as it means the
> L1 VMM is conditioned to reload its LDTR in order to function properly on
> bare metal.
>
> Fixes: 4704d0befb07 ("KVM: nVMX: Exiting from L2 to L1")
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Reiji Watanabe <reijiw@...gle.com>