Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1172

vmsw — Virtual Machine Switch
vmsw.0
Format:
vmsw.1
This instruction sets the PSR.vm bit to the specified value. This instruction can be used
Description:
to implement transitions to/from virtual machine mode without the overhead of an
interruption.
If instruction address translation is enabled and the page containing the vmsw
instruction has access rights equal to 7, then the new value is written to the PSR.vm
bit. In the zero_form, PSR.vm is set to 0, and in the one_form, PSR.vm is set to 1.
Instructions after the vmsw instruction in the same instruction group may be executed
with the old or new value of PSR.vm. Instructions in subsequent instruction groups will
be executed with PSR.vm equal to the new value.
If the above conditions are not met, this instruction takes a Virtualization fault.
This instruction can only be executed at the most privileged level. This instruction
cannot be predicated.
Implementation of PSR.vm is optional. If it is not implemented, this instruction takes
Illegal Operation fault. If it is implemented but either virtual machine features or the
vmsw instruction are disabled, this instruction takes Virtualization fault when executed
at the most privileged level.
Operation: if (!implemented_vm())
illegal_operation fault();
if (PSR.cpl != 0)
privileged_operation_fault(0);
if (!(PSR.it == 1 && itlb_ar() == 7) || vm_disabled() || vmsw_disabled())
virtualization_fault();
if (zero_form) {
PSR.vm = 0;
}
else {
PSR.vm = 1;
}
Illegal Operation fault
Interruptions:
Privileged Operation fault
Volume 3: Instruction Reference
Virtualization fault
vmsw
zero_form B8
one_form B8
3:273