Re: [Qemu-devel] [PATCH 3/5] target-i386: call x86_cpu_realize() after APIC is initialized.

[Igor Mammedov <imammedo@redhat.com>]

On 07/09/2012 02:57 PM, Andreas Färber wrote:
> Am 09.07.2012 12:59, schrieb igor:
>> On 06/20/2012 03:35 PM, Andreas Färber wrote:
>>> Am 20.06.2012 14:59, schrieb Igor Mammedov:
>>>> It's not correct to make CPU runnable (i.e. calling x86_cpu_realize())
>>>> when not all properties are set (APIC in this case).
>>>>
>>>> Fix it by calling x86_cpu_realize() at board level after APIC is
>>>> initialized, right before cpu_reset().
>>>>
>>>> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
>>>> ---
>>>>    hw/pc.c              |    1 +
>>>>    target-i386/helper.c |    2 --
>>>>    2 files changed, 1 insertion(+), 2 deletions(-)
>>>>
>>>> diff --git a/hw/pc.c b/hw/pc.c
>>>> index 8368701..8a662cf 100644
>>>> --- a/hw/pc.c
>>>> +++ b/hw/pc.c
>>>> @@ -948,6 +948,7 @@ static X86CPU *pc_new_cpu(const char *cpu_model)
>>>>            env->apic_state = apic_init(env, env->cpuid_apic_id);
>>>>        }
>>>>        qemu_register_reset(pc_cpu_reset, cpu);
>>>> +    x86_cpu_realize(OBJECT(cpu), NULL);
>>>>        pc_cpu_reset(cpu);
>>>>        return cpu;
>>>>    }
>>>> diff --git a/target-i386/helper.c b/target-i386/helper.c
>>>> index c52ec13..b38ea7f 100644
>>>> --- a/target-i386/helper.c
>>>> +++ b/target-i386/helper.c
>>>> @@ -1161,8 +1161,6 @@ X86CPU *cpu_x86_init(const char *cpu_model)
>>>>            return NULL;
>>>>        }
>>>>
>>>> -    x86_cpu_realize(OBJECT(cpu), NULL);
>>>> -
>>>>        return cpu;
>>>>    }
>>>>
>>>
>>> This will require changes in linux-user and possibly bsd-user. Having a
>>> cpu_realize() would probably help with avoiding #ifdef'ery.
>>> Unfortunately deriving CPUState from DeviceState proves a bit difficult
>>> in the meantime (it worked at one point, now there's lots of circular
>>> header dependencies), and realize support for Object got stopped.
>>>
>> As alternative to keep, I could leave x86_cpu_realize() in
>> cpu_x86_init() and keep pc_cpu_reset() in pc_new_cpu(). That will result
>> in calling cpu_reset() 3 instead of 2 times.
>> Later when apic_init is moved inside cpu.c, a pc_cpu_reset() in
>> pc_new_cpu() would be unnecessary and could be cleaned up then.
>
> Let me explain in more detail what I was thinking about: cpu_init() and
> cpu_x86_init() today return an initialized/realized object. I don't want
> bugs to creep into the user emulators because someone is not aware that
> x86 is semantically differing from all other targets.
>
> What I did for a qemu-rl78 machine is to inline cpu_rl78_init() so that
> I could put code in between, i.e., for x86: object_new(), APIC/BSP
> stuff, x86_cpu_realize(). That way any addition to the realize function
> will still affect the user emulators.
> The downside is that when we add x86 CPU subclasses we'd have to
> remember to update two places. The solution to that would be to split
> out a x86_cpu_new() function used from cpu_x86_init() and wherever you
> need it for the PC machine. Then the code is still maintainable in one
> central place and you get to do your APIC cleanups, and we don't depend
> on a central realize implementation or device parent, what do you think?

If you mean x86_cpu_new() == pc_new_cpu() that calls cpu_x86_init(),
then I'd like get rid of pc_new_cpu() completely, eventually replacing it by
cpu_x86_init() in hw/pc.c:pc_cpus_init(), something like this:

-static X86CPU *pc_new_cpu(const char *cpu_model)
-{
-    X86CPU *cpu;
-    CPUX86State *env;
-
-    cpu = cpu_x86_init(cpu_model);
-    if (cpu == NULL) {
-        fprintf(stderr, "Unable to find x86 CPU definition\n");
-        exit(1);
-    }
-    env = &cpu->env;
-    if ((env->cpuid_features & CPUID_APIC) || smp_cpus > 1) {
-        env->apic_state = apic_init(env, env->cpuid_apic_id);
-    }
-    cpu_reset(CPU(cpu));
-    return cpu;
-}
-
  void pc_cpus_init(const char *cpu_model)
  {
      int i;
@@ -950,7 +932,7 @@ void pc_cpus_init(const char *cpu_model)
      }

      for(i = 0; i < smp_cpus; i++) {
-        pc_new_cpu(cpu_model);
+        cpu_x86_init(cpu_model);
      }
  }

goal I'm aiming at is to have a working cpu object that could be created
using qdev_device_add without any adhoc calls. So in the end cpu_x86_init()
should become object_new(x86_cpu), [set props], realize() and nothing else.
And maybe in some far future removing cpu_init -> cpu_x86_init() completely.
That would give us a single implementation of CPU one place (cpu.c)
-- 
-----
Regards,
  Igor