Encoding:

Format:

MTGC0 rt, rs, sel

Purpose:

Move to Guest Coprocessor 0

To move the contents of a general register to a guest coprocessor 0 register.

Description:

 Guest.CPR[0, rs, sel] = GPR[rt]

The contents of general register rt are loaded into the guest context coprocessor 0 register specified by the combination of rs and sel. Not all guest context coprocessor 0 registers support the sel field. In those instances, the sel field must be set to zero.

When the guest context coprocessor 0 destination register specified is the EntryLo0 or the EntryLo1 register, bits

31:30 appear as the RI/XI fields of the destination register. This feature supports 32-bit addressing mode compatibility on a MIPS64 system.

Restrictions:

The results are UNDEFINED if guest context coprocessor 0 does not contain the register as specified by rs and sel or the destination register is the Guest.Count register, which is read-only

The guest context does notimplementthe Virtualization Module. Use of this instruction in guest-kernel mode will result in a Reserved Instruction exception, taken in guest mode.

MTGC0 must behave exactly the same as the corresponding guest MTC0instruction, exceptthatit will not cause exceptions that are specific to guest, such as GPSI and GSFC. Specifically, if the guest register is replicated in guest context, then the write must complete, if the register is Reserved for Architecture/Implementation or is Not Available, the write is ignored, if the register is Shared (such as WatchHi) then the write always completes but does not effect fields invisible to guest.

In a 64-bit processor, the MTGC0 instruction writes all 64 bits of register rt into the guest context coprocessor register specified by rd and sel if that register is a 64-bit register.

If access to Coprocessor 0 is not enabled, a Coprocessor Unusable Exception is signaled.

Operation:

if IsCoprocessorEnabled(0) then
   if (Config3VZ = 0) then
      SignalException(ReservedInstruction, 0)
      break
   endif
   data = GPR[rt]
   reg = rs
   if (reg,sel = EntryLo1 or reg,sel = EntryLo0) then
      Guest.CPR[0,reg,sel]29..0 = data29..0
      Guest.CPR[0,reg,sel]63 = data31
      Guest.CPR[0,reg,sel]62 = data30
      Guest.CPR[0,reg,sel]61:30 = 032
   else if (Width(CPR[0,reg,sel]) = 64) then
      Guest.CPR[0,reg,sel] = data
   else
   endif
else
   SignalException(CoprocessorUnusable, 0)
endif

Exceptions:

Coprocessor Unusable

Reserved Instruction