Re: [PATCH][QEMU] Use a separate device for in-kernel PIT

[Anthony Liguori <aliguori@us.ibm.com>]

Dor Laor wrote:
> On Wed, 2008-03-12 at 12:38 -0500, Anthony Liguori wrote:
>   
>> Part of the feedback we received from Fabrice about the KVM patches
>> for QEMU
>> is that we should create a separate device for the in-kernel APIC to
>> avoid
>> having lots of if (kvm_enabled()) within the APIC code that were
>> difficult to
>> understand why there were needed.
>>
>> This patch separates the in-kernel PIT into a separate device.  It
>> also
>> introduces some configure logic to only compile in support for the
>> in-kernel
>> PIT if it's available.
>>
>> The result of this is that we now only need a single if
>> (kvm_enabled()) to
>> determine which device to use.  Besides making it more upstream
>> friendly, I
>> think this makes the code much easier to understand.
>>
>>     
>
> Seems like a good idea.
>
> [snip]
> ..
>
>
>
>   
>> +static void pit_reset(void *opaque)
>> +{
>> +    PITState *pit = opaque;
>> +    PITChannelState *s;
>> +    int i;
>> +
>> +    for(i = 0;i < 3; i++) {
>> +        s = &pit->channels[i];
>> +        s->mode = 3;
>> +        s->gate = (i != 2);
>> +        pit_load_count(s, 0);
>> +    }
>> +}
>> +
>>     
>
> Seems like pit_reset won't change the in-kernel pit state.
>   

Yeah, that seemed suspicious to me too.  I didn't want to change the 
existing behavior though for fear of introducing regressions.  Perhaps 
Sheng can comment on whether it's necessary to even have a reset handler 
in userspace?

Regards,

Anthony Liguori

> Actually this should handled as a part of more general reset ioctl to
> all of kvm's in-kernel devices.
>
> Cheers,
> Dor
>
>   


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