[libvirt] [PATCH 3/3] qemu: hyperv: Add support for reference time couter enlightenment

Peter Krempa pkrempa at redhat.com
Fri Feb 7 13:58:19 UTC 2014


On 02/07/14 12:03, Paolo Bonzini wrote:
> Il 05/02/2014 12:02, Peter Krempa ha scritto:
>> Add a new <timer> for the HyperV reference time counter enlightenment
>> for Windows guests.
>>
>> This feature provides a paravirtual approach to track timer events for
>> the quest (similar to kvmclock).
> 
> RTC can be confusing because the same acronym expands to both "real-time
> clock" and "reference time counter".

I was confused too, when I saw it the first time.

> 
> By the way, the same <timer> will drive two things: the reference time
> counter, and the reference TSC page.  In current kernels, the reference
> TSC page just tells the guest "use the reference time counter", but this
> can be changed in the future without breaking the guest ABI.

That's right, the feature is actually backwards compatible to a great
extent and even tolerates the iTSC vanishing at migration. This makes
our lives really easier.

> 
> So, what about naming it hv_clock or hyperv_clock or hyperv_ref?

hyperv_clock then. DanPB was concerned that hv could mean "hypervisor"
to some people.

> 
> Paolo
> 

Thanks for the feedback.

Peter


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