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RE: [Xen-devel] Time goes backwards in dom0 in xen-unstable

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] Time goes backwards in dom0 in xen-unstable
From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Date: Wed, 15 Apr 2009 15:51:37 +0800
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Thread-topic: [Xen-devel] Time goes backwards in dom0 in xen-unstable
>From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx] 
>Sent: 2009年4月15日 15:44
>On 15/04/2009 00:31, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:
>> That missing feature
>> is to emulate RTC interrupt with IRQ8 replaced by HPET if
>> using legacy replacement mode. We're adding that emulation
>> now and hopefully get it ready in several days and in final
>> Xen 3.4 release.
>It's a bit late for 3.4 really. We'll be past -rc2 by the time 
>you get this
>patch out so it's missed the boat.

We revised our plan here, after realizing not-negligible effort to
enable RTC emulation. Instead we want to turn to an alternative
that hpet broadcast is always enabled once available (current
situation is to always give up if no MSI delivery support), and
then disable it on the fly (disable HPET interrupt and reduce
max_cstate to a level not requiring broadcast) once detecting
user trying to enable UIE/PIE/AIE on RTC. That way is far 
simpler and makes cpuidle really available on most platforms
with HPET (true for most with VT support), in the meantime
not breaking occasional usage on RTC interrupt.

Will you accept such patch which handles mostly about policy? :-)
We'll try to send it out today.

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