Re: [Qemu-devel] Rethinking missed tick catchup

[Gleb Natapov]

On Wed, Sep 12, 2012 at 05:42:58PM +0200, Jan Kiszka wrote:
> On 2012-09-12 17:06, Gleb Natapov wrote:
> >>>> Are there other issues with reinjection that people are aware of?  Does
> >>>> anything seem obviously wrong with the above?
> >>>
> >>> We should take the chance and design everything in a way that the HPET
> >>> can finally be (left) enabled.
> >>
> >> I thought the issue with the HPET was access frequency and the cost of
> >> heavy weight exits.
> >>
> >> I don't have concrete data here.  I've only heard it second hand.  Can
> >> anyone comment more?
> >>
> > There is no any reason whatsoever to emulate HPET for Windows. It will
> > make it slower. Hyper-V does not emulate it. For proper time support in
> > Windows we need to implement relevant part of Hyper-V spec.
> 
> There are two reasons to do it nevertheless:
> 
>  - QEMU is not Hyper-V. We are emulating the HPET already, and we
>    expose it by default. So we should do it properly.
> 
>  - The time drift fix for the RTC is still a hack. Adding a second user
>    would force us to finally clean it up.
> 
I am not saying we should not emulate HPET in QEMU,  I am saying there
is not reason to emulate it for Windows :)

--
                        Gleb.