MFC r358848: Untangle TPR shadowing and APIC virtualization.
This speeds up Windows guests tremendously. The patch does: Add a new tuneable 'hw.vmm.vmx.use_tpr_shadowing' to disable TLP shadowing. Also add 'hw.vmm.vmx.cap.tpr_shadowing' to be able to query if TPR shadowing is used. Detach the initialization of TPR shadowing from the initialization of APIC virtualization. APIC virtualization still needs TPR shadowing, but not vice versa. Any CPU that supports APIC virtualization should also support TPR shadowing. When TPR shadowing is used, the APIC page of each vCPU is written to the VMCS_VIRTUAL_APIC field of the VMCS so that the CPU can write directly to the page without intercept. On vm exit, vlapic_update_ppr() is called to update the PPR.
Submitted by: Yamagi Burmeister
Reviewed by: grehan
Differential Revision: https://reviews.freebsd.org/D22942
Approved by: bz (mentor)
Tested by: Jason Tubnor