Re: [Qemu-devel] [PATCH v3 12/19] apic: move MAX_APICS check to 'apic' class

[Bandan Das <bsd@redhat.com>]

Eduardo Habkost <ehabkost@redhat.com> writes:

> On Wed, Jul 13, 2016 at 06:47:20PM -0400, Bandan Das wrote:
>> Igor Mammedov <imammedo@redhat.com> writes:
>> 
>> > MAX_APICS is only used by child 'apic' class and not
>> > by its parent TYPE_APIC_COMMON or any other derived
>> > class.
>> > Move check into end user 'apic' class so it won't
>> > get in the way of other APIC implementations
>> > if they support more then MAX_APICS.
>> >
>> > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
>> > ---
>> >  hw/intc/apic.c                  | 10 ++++++++++
>> >  hw/intc/apic_common.c           |  8 --------
>> >  include/hw/i386/apic_internal.h |  4 +---
>> >  3 files changed, 11 insertions(+), 11 deletions(-)
>> >
>> > diff --git a/hw/intc/apic.c b/hw/intc/apic.c
>> > index e1ab935..b0d237b 100644
>> > --- a/hw/intc/apic.c
>> > +++ b/hw/intc/apic.c
>> > @@ -28,7 +28,9 @@
>> >  #include "trace.h"
>> >  #include "hw/i386/pc.h"
>> >  #include "hw/i386/apic-msidef.h"
>> > +#include "qapi/error.h"
>> >  
>> > +#define MAX_APICS 255
>> >  #define MAX_APIC_WORDS 8
>> >  
>> >  #define SYNC_FROM_VAPIC                 0x1
>> > @@ -869,6 +871,14 @@ static const MemoryRegionOps apic_io_ops = {
>> >  static void apic_realize(DeviceState *dev, Error **errp)
>> >  {
>> >      APICCommonState *s = APIC_COMMON(dev);
>> > +    static int apic_no;
>> 
>> Can this be a global ? I understand there are no other users but
>> maybe it fits alongside local_apics.
>
> The variable is removed by the next patch. :)
>
>> 
>> > +    if (apic_no >= MAX_APICS) {
>> > +        error_setg(errp, "%s initialization failed.",
>> > +                   object_get_typename(OBJECT(dev)));
>> > +        return;
>> > +    }
>> > +    s->idx = apic_no++;
>> 
>> Is there a possibility of a race here with the apic removal path ?
>
> If there's that possibility: 1) it was already in
> apic_common_realize(); 2) it is removed by patch 13/19.

Ugh! Stupid me :) Yep, thanks for pointing that out.

>> 
>> Bandan
>> 
>> >      memory_region_init_io(&s->io_memory, OBJECT(s), &apic_io_ops, s, "apic-msi",
>> >                            APIC_SPACE_SIZE);
>> > diff --git a/hw/intc/apic_common.c b/hw/intc/apic_common.c
>> > index e6eb694..fd425d1 100644
>> > --- a/hw/intc/apic_common.c
>> > +++ b/hw/intc/apic_common.c
>> > @@ -299,14 +299,6 @@ static void apic_common_realize(DeviceState *dev, Error **errp)
>> >      APICCommonState *s = APIC_COMMON(dev);
>> >      APICCommonClass *info;
>> >      static DeviceState *vapic;
>> > -    static int apic_no;
>> > -
>> > -    if (apic_no >= MAX_APICS) {
>> > -        error_setg(errp, "%s initialization failed.",
>> > -                   object_get_typename(OBJECT(dev)));
>> > -        return;
>> > -    }
>> > -    s->idx = apic_no++;
>> >  
>> >      info = APIC_COMMON_GET_CLASS(s);
>> >      info->realize(dev, errp);
>> > diff --git a/include/hw/i386/apic_internal.h b/include/hw/i386/apic_internal.h
>> > index 74fe935..5d3be9a 100644
>> > --- a/include/hw/i386/apic_internal.h
>> > +++ b/include/hw/i386/apic_internal.h
>> > @@ -120,8 +120,6 @@
>> >  #define VAPIC_ENABLE_BIT                0
>> >  #define VAPIC_ENABLE_MASK               (1 << VAPIC_ENABLE_BIT)
>> >  
>> > -#define MAX_APICS 255
>> > -
>> >  typedef struct APICCommonState APICCommonState;
>> >  
>> >  #define TYPE_APIC_COMMON "apic-common"
>> > @@ -175,7 +173,7 @@ struct APICCommonState {
>> >      uint32_t initial_count;
>> >      int64_t initial_count_load_time;
>> >      int64_t next_time;
>> > -    int idx;
>> > +    int idx; /* not actually common, used only by 'apic' derived class */
>> >      QEMUTimer *timer;
>> >      int64_t timer_expiry;
>> >      int sipi_vector;