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    Subject[PATCH v2 22/46] KVM: VMX: Remove direct write to vcpu->arch.cr0 during vCPU RESET/INIT
    From
    Remove a bogus write to vcpu->arch.cr0 that immediately precedes
    vmx_set_cr0() during vCPU RESET/INIT. For RESET, this is a nop since
    the "old" CR0 value is meaningless. But for INIT, if the vCPU is coming
    from paging enabled mode, crushing vcpu->arch.cr0 will cause the various
    is_paging() checks in vmx_set_cr0() to get false negatives.

    For the exit_lmode() case, the false negative is benign as vmx_set_efer()
    is called immediately after vmx_set_cr0().

    For EPT without unrestricted guest, the false negative will cause KVM to
    unnecessarily run with CR3 load/store exiting. But again, this is
    benign, albeit sub-optimal.

    Reviewed-by: Reiji Watanabe <reijiw@google.com>
    Signed-off-by: Sean Christopherson <seanjc@google.com>
    ---
    arch/x86/kvm/vmx/vmx.c | 5 +----
    1 file changed, 1 insertion(+), 4 deletions(-)

    diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
    index 02aec75ec6f6..ed631564c651 100644
    --- a/arch/x86/kvm/vmx/vmx.c
    +++ b/arch/x86/kvm/vmx/vmx.c
    @@ -4383,7 +4383,6 @@ static void init_vmcs(struct vcpu_vmx *vmx)
    static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
    {
    struct vcpu_vmx *vmx = to_vmx(vcpu);
    - u64 cr0;

    if (!init_event)
    init_vmcs(vmx);
    @@ -4454,9 +4453,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)

    kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu);

    - cr0 = X86_CR0_NW | X86_CR0_CD | X86_CR0_ET;
    - vmx->vcpu.arch.cr0 = cr0;
    - vmx_set_cr0(vcpu, cr0); /* enter rmode */
    + vmx_set_cr0(vcpu, X86_CR0_NW | X86_CR0_CD | X86_CR0_ET);
    vmx_set_cr4(vcpu, 0);
    vmx_set_efer(vcpu, 0);

    --
    2.32.0.93.g670b81a890-goog
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