Messages in this thread | | | Subject | Re: [PATCH v5 4/5] KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL | From | KarimAllah Ahmed <> | Date | Wed, 31 Jan 2018 21:01:33 +0100 |
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On 01/31/2018 08:53 PM, Jim Mattson wrote: > On Wed, Jan 31, 2018 at 11:37 AM, KarimAllah Ahmed <karahmed@amazon.de> 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..."
but save_spec_ctrl_on_exit is also set for L2 write. So once L2 writes to it, this condition will be true and then the bitmap will be updated.
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