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    SubjectRe: [PATCH v2 1/2] KVM: VMX: Don't advertise EPT switching if EPT itself is not exposed
    Following the same line of reasoning, what if
    vmx->nested.nested_vmx_secondary_ctls_high is 0 after clearing
    SECONDARY_EXEC_ENABLE_VMFUNC? Does it make sense to report
    CPU_BASED_ACTIVATE_SECONDARY_CONTROLS if we don't actually support any
    of the secondary controls?

    Reviewed-by: Jim Mattson <jmattson@google.com>

    On Mon, Oct 16, 2017 at 9:03 PM, Wanpeng Li <kernellwp@gmail.com> wrote:
    > From: Wanpeng Li <wanpeng.li@hotmail.com>
    >
    > I can use vmxcap tool to observe "EPTP Switching yes" even if EPT is not
    > exposed to L1.
    >
    > EPT switching is advertised unconditionally since it is emulated, however,
    > it can be treated as an extended feature for EPT and it should not be
    > advertised if EPT itself is not exposed. This patch fixes it.
    >
    > Cc: Paolo Bonzini <pbonzini@redhat.com>
    > Cc: Radim Krčmář <rkrcmar@redhat.com>
    > Cc: Jim Mattson <jmattson@google.com>
    > Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
    > ---
    > v1 -> v2:
    > * don't advertise "EPT VM Functions" in secondary processor-based VM-execution
    > controls if we don't actually support any VM Functions.
    >
    > arch/x86/kvm/vmx.c | 8 ++++++--
    > 1 file changed, 6 insertions(+), 2 deletions(-)
    >
    > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
    > index c460b0b..a6861ca 100644
    > --- a/arch/x86/kvm/vmx.c
    > +++ b/arch/x86/kvm/vmx.c
    > @@ -2842,8 +2842,12 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
    > * Advertise EPTP switching unconditionally
    > * since we emulate it
    > */
    > - vmx->nested.nested_vmx_vmfunc_controls =
    > - VMX_VMFUNC_EPTP_SWITCHING;
    > + if (enable_ept) {
    > + vmx->nested.nested_vmx_vmfunc_controls =
    > + VMX_VMFUNC_EPTP_SWITCHING;
    > + } else
    > + vmx->nested.nested_vmx_secondary_ctls_high &=
    > + ~SECONDARY_EXEC_ENABLE_VMFUNC;
    > }
    >
    > /*
    > --
    > 2.7.4
    >

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