Specifications

Intel
®
64 and IA-32 Architectures Software Developer’s Manual Documentation Changes 266
Documentation Changes
The following software usage is consistent with these limitations:
• VMCLEAR should be executed for a VMCS before it is used for VM entry for the first
time.
• VMLAUNCH should be used for the first VM entry using a VMCS after VMCLEAR has
been executed for that VMCS.
• VMRESUME should be used for any subsequent VM entry using a VMCS (until the
next execution of VMCLEAR for the VMCS).
It is expected that, in general, VMRESUME will have lower latency than VMLAUNCH.
Since “migrating” a VMCS from one logical processor to another requires use of
VMCLEAR (see Section 21.10.1), which sets the launch state of the VMCS to “clear”, such
migration requires the next VM entry to be performed using VMLAUNCH. Software devel-
opers can avoid the performance cost of increased VM-entry latency by avoiding unnec-
essary migration of a VMCS from one logical processor to another.
...