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Date: Tue, 22 Mar 2011 05:40:21 -0400 (EDT)
From: Ulrich Obergfell <uobergfe@redhat.com>
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Subject: [Qemu-devel] Re: [PATCH 1/3] alleviate time drift with HPET
	periodic timers
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To: Jan Kiszka <jan.kiszka@web.de>
Cc: aliguori@us.ibm.com, qemu-devel@nongnu.org, kvm <kvm@vger.kernel.org>, gcosta@redhat.com


>> Part 1 of the patch implements the following QEMU command line option.
>>
>> -hpet [device=none|present][,driftfix=none|slew]
> 
> Just define driftfix as property of the hpet device. That way it can be
> controlled both globally (-global hpet.driftfix=...) and per hpet block
> (once we support instantiating >1 of them).


Many Thanks Jan,

I started investigating code changes. I'm thinking of ...

- adding a new field to the HPETState structure.

    uint32_t driftfix;

- adding the property 'driftfix' to the DeviceInfo structure.

    DEFINE_PROP_BIT("driftfix", HPETState, driftfix, 0, false)

  Using a single bit so that the option syntax would be, e.g.:

    -global hpet.driftfix=on     (Default is 'off')

- Replace all 'if (hpet_driftfix ...)' by:

    if ((HPETState)s->driftfix ...)


Regards,

Uli