Re: [Qemu-devel] [PATCH v4 0/3] bugs fix for hpet

[Paolo Bonzini <pbonzini@redhat.com>]

Il 04/09/2013 07:29, liu ping fan ha scritto:
> On Tue, Sep 3, 2013 at 7:17 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> Il 02/09/2013 09:06, Liu Ping Fan ha scritto:
>>> note: I rebase it onto Stefan's net-next tree, since pc-1.7 has already been defined there.
>>>
>>> v4:
>>>   use standard compat property to set hpet's interrupt compatibility
>>>
>>> v3:
>>>   change hpet interrupt capablity on board's demand
>>>
>>>
>>> Liu Ping Fan (3):
>>>   hpet: inverse polarity when pin above ISA_NUM_IRQS
>>>   hpet: entitle more irq pins for hpet
>>>   pc-1.6: add compatibility for hpet intcap on pc-*-1.6
>>>
>>>  hw/timer/hpet.c      | 27 +++++++++++++++++++++++----
>>>  include/hw/i386/pc.h |  5 +++++
>>>  2 files changed, 28 insertions(+), 4 deletions(-)
>>>
>>
>> Looks good.  But I have one question; should this be changed for PIIX
>> too, or should the 1.7 PIIX machine keep the old behavior?  (I have no
>> idea).
>>
> Your suspicion is right.  When going through PIIX4 spec, I found that
> the chipset was without ioapic integrated. So there is divergence for
> the compatibility of pc-piix-* and pc-q35-*.  Can I code the hpet's
> compatiblity in pc-piix-1.7 to resolve this?

You could do something like what people suggested earlier in the review.
 Change sysbus_try_create_simple to
qdev_try_create/sysbus_mmio_map/qdev_init in pc_basic_device_init (this
is one patch, going before v4 3/3).  Then add a new argument to
pc_basic_device_init, and set the intcap property if the new argument is
nonzero (another patch, going before v4 3/3; where the new argument is
always 0).  Finally, piix can pass 4 for the new argument, while q35 can
keep passing 0 (squashed in v4 3/3).

In other words, PIIX hardcodes the value 4, while Q35 uses compat
properties.

I still have a doubt.  Can the PIIX HPET use interrupt 8?  If so, this
won't work and we have to go back to the drawing board.  But if it can
use interrupt 2 only, it will be okay.

Paolo