accel: add init_accel_cpu for adapting accel behavior to CPU type

while on x86 all CPU classes can use the same set of TCGCPUOps,
on ARM the right accel behavior depends on the type of the CPU.

So we need a way to specialize the accel behavior according to
the CPU. Therefore, add a second initialization, after the
accel_cpu->cpu_class_init, that allows to do this.

Signed-off-by: Claudio Fontana <cfontana@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210322132800.7470-24-cfontana@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

accel/accel-common.c

@@ -54,10 +54,23 @@ static void accel_init_cpu_int_aux(ObjectClass *klass, void *opaque)
     CPUClass *cc = CPU_CLASS(klass);
     AccelCPUClass *accel_cpu = opaque;
 
+    /*
+     * The first callback allows accel-cpu to run initializations
+     * for the CPU, customizing CPU behavior according to the accelerator.
+     *
+     * The second one allows the CPU to customize the accel-cpu
+     * behavior according to the CPU.
+     *
+     * The second is currently only used by TCG, to specialize the
+     * TCGCPUOps depending on the CPU type.
+     */
     cc->accel_cpu = accel_cpu;
     if (accel_cpu->cpu_class_init) {
         accel_cpu->cpu_class_init(cc);
     }
+    if (cc->init_accel_cpu) {
+        cc->init_accel_cpu(accel_cpu, cc);
+    }
 }
 
 /* initialize the arch-specific accel CpuClass interfaces */

include/hw/core/cpu.h

@@ -192,6 +192,12 @@ struct CPUClass {
 
     /* when TCG is not available, this pointer is NULL */
     struct TCGCPUOps *tcg_ops;
+
+    /*
+     * if not NULL, this is called in order for the CPUClass to initialize
+     * class data that depends on the accelerator, see accel/accel-common.c.
+     */
+    void (*init_accel_cpu)(struct AccelCPUClass *accel_cpu, CPUClass *cc);
 };
 
 /*

target/i386/tcg/tcg-cpu.c

@@ -69,11 +69,17 @@ static struct TCGCPUOps x86_tcg_ops = {
 #endif /* !CONFIG_USER_ONLY */
 };
 
-static void tcg_cpu_class_init(CPUClass *cc)
+static void tcg_cpu_init_ops(AccelCPUClass *accel_cpu, CPUClass *cc)
 {
+    /* for x86, all cpus use the same set of operations */
     cc->tcg_ops = &x86_tcg_ops;
 }
 
+static void tcg_cpu_class_init(CPUClass *cc)
+{
+    cc->init_accel_cpu = tcg_cpu_init_ops;
+}
+
 /*
  * TCG-specific defaults that override all CPU models when using TCG
  */