Re: [Qemu-devel] [PATCH v3 1/5] hpet 'driftfix': add hooks required to detect coalesced interrupts (x86 apic only)

[Blue Swirl <blauwirbel@gmail.com>]

On Fri, Apr 29, 2011 at 12:45 PM, Ulrich Obergfell <uobergfe@redhat.com> wrote:
>
>> On 2011-04-28 20:51, Blue Swirl wrote:
>>> On Thu, Apr 28, 2011 at 5:24 PM, Ulrich Obergfell wrote:
>>>> 'target_get_irq_delivered' and 'target_reset_irq_delivered' contain
>>>> entry addresses of functions that are utilized by update_irq() to
>>>> detect coalesced interrupts. apic code loads these pointers during
>>>> initialization.
>>>
>>> I'm not so happy with this approach, but probably then the i386
>>> dependencies can be removed from RTC and it can be compiled only once
>>> for all targets.
>>
>> This whole series is really the minimalistic approach. The callbacks
>> defined here must remain a temporary "shortcut". Just like proper
>> abstraction of periodic tick compensation for reuse in other timers has
>> to be added later on. And the limitation to edge-triggered legacy HPET
>> INTs has to be removed.
>
> Since QEMU doesn't have a generic infrastructure to track interrupt
> delivery, I decided to reuse something that is currently available.
> The only mechanism that I'm aware of is the one that is utilized by
> RTC code ('rtc_td_hack'), i.e. apic_get_irq_delivered() etc.

I think your approach is slightly better (while not the best possible
one), so it should be used also for RTC.

Some more comments:
- instead of global variables, there could be a setter function (maybe inline)
- pc.h would be a better place instead of sysemu.h

> The changes that would be introduced by part 1/5 and part 4/5 of
> this patch series could be replaced if a generic infrastructure
> to track interrupt delivery becomes available.

OK.