Re: [Qemu-devel] [RFC 01/18] pc: create "PC" device class

[Anthony Liguori <anthony@codemonkey.ws>]

Eduardo Habkost <ehabkost@redhat.com> writes:

> On Thu, Oct 04, 2012 at 08:46:46AM -0500, Anthony Liguori wrote:
>> Eduardo Habkost <ehabkost@redhat.com> writes:
>> 
>> > We can make it a child of a generic "machine" class later, but right now
>> > a "PC" class is needed to allow global-properties to control some
>> > details of CPU creation on the PC code.
>> >
>> > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
>> > ---
>> >  hw/pc.c | 18 ++++++++++++++++++
>> >  hw/pc.h |  6 ++++++
>> >  2 files changed, 24 insertions(+)
>> >
>> > diff --git a/hw/pc.c b/hw/pc.c
>> > index 7e7e0e2..9b68282 100644
>> > --- a/hw/pc.c
>> > +++ b/hw/pc.c
>> > @@ -550,6 +550,24 @@ static void bochs_bios_write(void *opaque, uint32_t addr, uint32_t val)
>> >      }
>> >  }
>> >  
>> > +typedef struct PC {
>> > +    DeviceState parent_obj;
>> > +} PC;
>> 
>> So the general problem with this approach is that it strays from
>> modeling hardware.
>
> True, it's not modelling hardware. It's controlling the behavior of the
> QEMU code that set APIC IDs, because we need to keep the old behavior on
> old machine-types.
>
>> 
>> I guess I'm confused why we're not just adding an apic_id property to
>> the CPU objects and setting that via the normal QOM accessors.
>> 
>> Wouldn't that solve the problem?
>> 
>
> It wouldn't solve the problem (although it can make the code look
> better).
>
> The problem is not setting the APIC ID, is controlling the code that
> generates the APIC IDs. I don't care too much where that code would live
> (it could be inside cpu.c or helper.c), but it still needs a flag where
> old machine-types tell it "please keep the old behavior for
> compatibility".

Can you just add a flag to pc_init1 and set the apic_id property
according to that flag?

Then you simply add a pc_init_post_1_3 and pc_init_pre_1_3 that calls
pc_init1 with the appropriate flag value.

Regards,

Anthony Liguori

>
>
>> Regards,
>> 
>> Anthony Liguori
>> 
>> > +
>> > +static const TypeInfo pc_type_info = {
>> > +    .name = TYPE_PC_MACHINE,
>> > +    .parent = TYPE_DEVICE,
>> > +    .instance_size = sizeof(PC),
>> > +    .class_size = sizeof(DeviceClass),
>> > +};
>> > +
>> > +static void pc_register_type(void)
>> > +{
>> > +    type_register_static(&pc_type_info);
>> > +}
>> > +
>> > +type_init(pc_register_type);
>> > +
>> >  int e820_add_entry(uint64_t address, uint64_t length, uint32_t type)
>> >  {
>> >      int index = le32_to_cpu(e820_table.count);
>> > diff --git a/hw/pc.h b/hw/pc.h
>> > index e4db071..77e898f 100644
>> > --- a/hw/pc.h
>> > +++ b/hw/pc.h
>> > @@ -102,6 +102,12 @@ void i8042_setup_a20_line(ISADevice *dev, qemu_irq *a20_out);
>> >  /* pc.c */
>> >  extern int fd_bootchk;
>> >  
>> > +#define TYPE_PC_MACHINE "PC"
>> > +#define PC(obj) \
>> > +    OBJECT_CHECK(PC, (obj), TYPE_PC_MACHINE)
>> > +struct PC;
>> > +typedef struct PC PC;
>> > +
>> >  void pc_register_ferr_irq(qemu_irq irq);
>> >  void pc_acpi_smi_interrupt(void *opaque, int irq, int level);
>> >  
>> > -- 
>> > 1.7.11.4
>
> -- 
> Eduardo