Re: [PATCH 2/3] [PATCH] kvmclock - the host part.

[Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org>]

Avi Kivity wrote:
> Anthony Liguori wrote:
>> Glauber de Oliveira Costa wrote:
>>  
>>> This is the host part of kvm clocksource implementation. As it does
>>> not include clockevents, it is a fairly simple implementation. We
>>> only have to register a per-vcpu area, and start writting to it 
>>> periodically.
>>>
>>> The area is binary compatible with xen, as we use the same 
>>> shadow_info structure.
>>>
>>> diff --git a/include/asm-x86/kvm_para.h b/include/asm-x86/kvm_para.h
>>> index c6f3fd8..abe412a 100644
>>> --- a/include/asm-x86/kvm_para.h
>>> +++ b/include/asm-x86/kvm_para.h
>>> @@ -1,5 +1,6 @@
>>>  #ifndef __X86_KVM_PARA_H
>>>  #define __X86_KVM_PARA_H
>>> +#include <xen/interface/xen.h>
>>>     
>>
>> Can we abstract that out into a neutral header instead of including 
>> the Xen headers directly in KVM.  Please rename the structure too to 
>> something neutral.
>>
>> Including something as generic as xen/interface/xen.h when CONFIG_XEN 
>> may not be set is not a good thing, I believe.
>>   
>
> Well, one of the motivations behind this is to actually supply a Xen 
> clock to Xen guests.  So maybe we can call the feature a "kvm 
> xenclock" instead and feel justified in including Xen headers.
>
> However, you are probably right in that we are getting into a 
> dependency and kconfig hell we do not yet deserve.  Not even 
> mentioning that CONFIG_XEN is a guest thing while kvmclock is also a 
> host thing.
>
> So we are probably better of using a non-Xen structure that 
> accidentally happens to be binary compatible with the Xen interface.  
> Stranger things have happened.

Yes, this is what I meant.  My concerns is dependencies and namespace 
pollution.  I think using the same interface is a very Good Thing.

Regards,

Anthony Liguori

> If we agree on this, please define _only_ the time-related parts so we 
> have a decoupled interface.  We'll need two msrs:  one for wc and one 
> for vcpu time.
>


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