cpu: Constify CPUState::cc (cached CPUClass pointer)

Various CPUState can share the same CPUClass parent,
and must not update its fields. Protect the CPUClass
by marking the CPUState pointer const.

Signed-off-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com>
Reviewed-by: Daniel Henrique Barboza <daniel.barboza@oss.qualcomm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Chao Liu <chao.liu.zevorn@gmail.com>
Message-ID: <20260705215729.62196-2-philmd@oss.qualcomm.com>

accel/tcg/cpu-exec.c

@@ -460,7 +460,7 @@ cpu_tb_exec(CPUState *cpu, TranslationBlock *itb, int *tb_exit)
          * counter hit zero); we must restore the guest PC to the address
          * of the start of the TB.
          */
-        CPUClass *cc = cpu->cc;
+        const CPUClass *cc = cpu->cc;
         const TCGCPUOps *tcg_ops = cc->tcg_ops;
 
         if (tcg_ops->synchronize_from_tb) {

accel/tcg/translate-all.c

@@ -575,7 +575,7 @@ void tb_check_watchpoint(CPUState *cpu, uintptr_t retaddr)
 void cpu_io_recompile(CPUState *cpu, uintptr_t retaddr)
 {
     TranslationBlock *tb;
-    CPUClass *cc;
+    const CPUClass *cc = cpu->cc;
     uint32_t n;
 
     tb = tcg_tb_lookup(retaddr);
@@ -591,7 +591,6 @@ void cpu_io_recompile(CPUState *cpu, uintptr_t retaddr)
      * to account for the re-execution of the branch.
      */
     n = 1;
-    cc = cpu->cc;
     if (cc->tcg_ops->io_recompile_replay_branch &&
         cc->tcg_ops->io_recompile_replay_branch(cpu, tb)) {
         cpu->neg.icount_decr.u16.low++;

gdbstub/gdbstub.c

@@ -578,7 +578,7 @@ static void gdb_register_feature(CPUState *cpu, int base_reg,
 
 static const char *gdb_get_core_xml_file(CPUState *cpu)
 {
-    CPUClass *cc = cpu->cc;
+    const CPUClass *cc = cpu->cc;
 
     /*
      * The CPU class can provide the XML filename via a method,

include/hw/core/cpu.h

@@ -480,7 +480,7 @@ struct CPUState {
     /*< private >*/
     DeviceState parent_obj;
     /* cache to avoid expensive CPU_GET_CLASS */
-    CPUClass *cc;
+    const CPUClass *cc;
     /*< public >*/
 
     int nr_threads;