From 094f44e92c3e3d540126df7326e407437a703f4e Mon Sep 17 00:00:00 2001
From: joevt <joevt@shaw.ca>
Date: Sat, 2 Mar 2024 01:45:24 -0800
Subject: [PATCH] ppcopcodes: Make MQ read only on non-601 CPUs.

---
 cpu/ppc/ppcopcodes.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/cpu/ppc/ppcopcodes.cpp b/cpu/ppc/ppcopcodes.cpp
index 4221932..b991dcb 100644
--- a/cpu/ppc/ppcopcodes.cpp
+++ b/cpu/ppc/ppcopcodes.cpp
@@ -927,7 +927,9 @@ void dppc_interpreter::ppc_mtspr() {
     }
 #endif
 
-    if (ref_spr == SPR::PVR) { // prevent writes to the read-only PVR
+    if (ref_spr == SPR::PVR || (
+        ref_spr == SPR::MQ && !is_601
+    )) { // prevent writes to the read-only registers
         return;
     }