Re: [Qemu-devel] [PATCH v2 1/7] apic: add global apic_get_class()

[Eduardo Habkost <ehabkost@redhat.com>]

On Thu, Sep 29, 2016 at 01:23:23PM +0200, Radim Krčmář wrote:
> Every configuration has only up to one APIC class and we'll be extending
> the class with a function that can be called without an instanced
> object, so a direct access to the class is convenient.
> 
> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
> ---
> v2: assert() instead of error_report() and exit() [Peter]
> ---
>  hw/intc/apic_common.c           | 11 +++++++++++
>  include/hw/i386/apic_internal.h |  3 +++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/hw/intc/apic_common.c b/hw/intc/apic_common.c
> index 14ac43c18666..a766f0efc805 100644
> --- a/hw/intc/apic_common.c
> +++ b/hw/intc/apic_common.c
> @@ -18,6 +18,7 @@
>   * License along with this library; if not, see <http://www.gnu.org/licenses/>
>   */
>  #include "qemu/osdep.h"
> +#include "qemu/error-report.h"
>  #include "qapi/error.h"
>  #include "qemu-common.h"
>  #include "cpu.h"
> @@ -296,6 +297,13 @@ static int apic_load_old(QEMUFile *f, void *opaque, int version_id)
>  
>  static const VMStateDescription vmstate_apic_common;
>  
> +APICCommonClass *apic_class;
> +
> +APICCommonClass *apic_get_class(void)
> +{
> +    return apic_class;
> +}
> +

This will break in case we need to look at the APIC class before
realizing the CPUs for any reason. Instead of adding a global
variable, what about moving the class name logic that's already
inside x86_cpu_apic_create() to the apic_get_class() function?
Then x86_cpu_apic_create() can simply call apic_get_class() too.

>  static void apic_common_realize(DeviceState *dev, Error **errp)
>  {
>      APICCommonState *s = APIC_COMMON(dev);
> @@ -306,6 +314,9 @@ static void apic_common_realize(DeviceState *dev, Error **errp)
>      info = APIC_COMMON_GET_CLASS(s);
>      info->realize(dev, errp);
>  
> +    assert(apic_class == info || !apic_class);
> +    apic_class = info;
> +
>      /* Note: We need at least 1M to map the VAPIC option ROM */
>      if (!vapic && s->vapic_control & VAPIC_ENABLE_MASK &&
>          ram_size >= 1024 * 1024) {
> diff --git a/include/hw/i386/apic_internal.h b/include/hw/i386/apic_internal.h
> index 06c4e9f6f95b..9ba8a5c87f90 100644
> --- a/include/hw/i386/apic_internal.h
> +++ b/include/hw/i386/apic_internal.h
> @@ -222,4 +222,7 @@ static inline int apic_get_bit(uint32_t *tab, int index)
>      return !!(tab[i] & mask);
>  }
>  
> +
> +APICCommonClass *apic_get_class(void);
> +
>  #endif /* QEMU_APIC_INTERNAL_H */
> -- 
> 2.10.0
> 

-- 
Eduardo