cpu: cache CPUClass in CPUState for hot code paths

The class cast checkers are quite expensive and always on (unlike the
dynamic case who's checks are gated by CONFIG_QOM_CAST_DEBUG). To
avoid the overhead of repeatedly checking something which should never
change we cache the CPUClass reference for use in the hot code paths.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220811151413.3350684-3-alex.bennee@linaro.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20220923084803.498337-3-clg@kaod.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 4 insertions, 5 deletions

diff --git a/cpu.c b/cpu.c
index 584ac78baf..14365e36f3 100644
--- a/cpu.c
+++ b/cpu.c
@@ -131,9 +131,8 @@ const VMStateDescription vmstate_cpu_common = {
 
 void cpu_exec_realizefn(CPUState *cpu, Error **errp)
 {
-#ifndef CONFIG_USER_ONLY
-    CPUClass *cc = CPU_GET_CLASS(cpu);
-#endif
+    /* cache the cpu class for the hotpath */
+    cpu->cc = CPU_GET_CLASS(cpu);
 
     cpu_list_add(cpu);
     if (!accel_cpu_realizefn(cpu, errp)) {
@@ -151,8 +150,8 @@ void cpu_exec_realizefn(CPUState *cpu, Error **errp)
     if (qdev_get_vmsd(DEVICE(cpu)) == NULL) {
         vmstate_register(NULL, cpu->cpu_index, &vmstate_cpu_common, cpu);
     }
-    if (cc->sysemu_ops->legacy_vmsd != NULL) {
-        vmstate_register(NULL, cpu->cpu_index, cc->sysemu_ops->legacy_vmsd, cpu);
+    if (cpu->cc->sysemu_ops->legacy_vmsd != NULL) {
+        vmstate_register(NULL, cpu->cpu_index, cpu->cc->sysemu_ops->legacy_vmsd, cpu);
     }
 #endif /* CONFIG_USER_ONLY */
 }