Re: [PATCH v5 4/5] KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL

[Jim Mattson]

On Wed, Jan 31, 2018 at 11:37 AM, KarimAllah Ahmed <karahmed@xxxxxxxxx> wrote:

> +
> +       if (to_vmx(vcpu)->save_spec_ctrl_on_exit) {
> +               nested_vmx_disable_intercept_for_msr(
> +                               msr_bitmap_l1, msr_bitmap_l0,
> +                               MSR_IA32_SPEC_CTRL,
> +                               MSR_TYPE_R | MSR_TYPE_W);
> +       }
> +

As this is written, L2 will never get direct access to this MSR until
after L1 writes it.  What if L1 never writes it? The condition should
really be something that captures, "if L0 is willing to yield this MSR
to the guest..."