MIPS; KVM: Convert exception entry to uasm

Convert the whole of locore.S (assembly to enter guest and handle
exception entry) to be generated dynamically with uasm. This is done
with minimal changes to the resulting code.

The main changes are:
- Some constants are generated by uasm using LUI+ADDIU instead of
  LUI+ORI.
- Loading of lo and hi are swapped around in vcpu_run but not when
  resuming the guest after an exit. Both bits of logic are now generated
  by the same code.
- Register MOVEs in uasm use different ADDU operand ordering to GNU as,
  putting zero register into rs instead of rt.
- The JALR.HB to call the C exit handler is switched to JALR, since the
  hazard barrier would appear to be unnecessary.

This will allow further optimisation in the future to dynamically handle
the capabilities of the CPU.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim KrÄmář <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/mips/include/asm/kvm_host.h

@@ -533,8 +533,12 @@ int kvm_mips_emulation_init(struct kvm_mips_callbacks **install_callbacks);
 /* Debug: dump vcpu state */
 int kvm_arch_vcpu_dump_regs(struct kvm_vcpu *vcpu);
 
-/* Trampoline ASM routine to start running in "Guest" context */
-extern int __kvm_mips_vcpu_run(struct kvm_run *run, struct kvm_vcpu *vcpu);
+extern int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu);
+
+/* Building of entry/exception code */
+void *kvm_mips_build_vcpu_run(void *addr);
+void *kvm_mips_build_exception(void *addr);
+void *kvm_mips_build_exit(void *addr);
 
 /* FPU/MSA context management */
 void __kvm_save_fpu(struct kvm_vcpu_arch *vcpu);