Intel Itanium 9150M, Manual

Page: 282 / 420

Volume 3: Instruction Reference 3:273
vmsw
vmsw — Virtual Machine Switch
Format: vmsw.0 zero_form B8
vmsw.1 one_form B8
Description:
This instruction sets the PSR.vm bit to the specified value. This instruction can be used
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;
}
Interruptions:
Illegal Operation fault Virtualization fault
Privileged Operation fault