On Thu, Sep 20, 2018 at 3:07 PM, Sean Christopherson <sean.j.christopherson@xxxxxxxxx> wrote: > vm_exit_controls_shadow, which is written by vm_exit_controls_init(), > is a shadow of the VM_EXIT_CONTROLS VMCS field. The shadow is used to > elide VMREADs and VMWRITEs to VM_EXIT_CONTROLS, i.e. we don't need to > VMREAD the field when toggling a bit and we can skip VMWRITE if the > desired value matches the shadow (and therefore matches the VMCS). > vm_exit_controls_shadow needs to be kept in sync with the VMCS field > at all times, otherwise we might incorrectly skip a VMWRITE, e.g. if > VM_EXIT_LOAD_IA32_EFER bit is set in the shadow but not the actual > VMCS field. When we switch to vmcs02 we need to re-initialize the > shadow because the shadow is per-VCPU, not per-VMCS. Perhaps the shadow should be per-VMCS?
