Re: using mapped vcpu_runstate_info in hvm guest

[Juergen Gross <juergen.gross@ts.fujitsu.com>]

On 20.11.2013 14:07, Jan Beulich wrote:
>>>> On 13.11.13 at 14:50, Juergen Gross <juergen.gross@ts.fujitsu.com> wrote:
>> I'm trying to obtain runstate information from the hypervisor in a hvm guest
>> via VCPUOP_register_runstate_memory_area. This works, but the information is
>> not completely suitable for a hvm guest:
>>
>> I can see the time summed up in the different states, but I'm not able to
>> deduce the exact time the current vcpu has been running. I see the time when
>> the last change to the running state happened (state_entry_time), but this
>> time is the hypervisor system time obtained via NOW(). I can't see how to
>> map this information to any time information available to the guest (e.g.
>> the tsc value).
>
> __update_vcpu_system_time() specifically considers the case of
> vTSC, so I'm not really clear what your problem here is. NOW()
> (and hence state_entry_time) are in ns units, and the information
> presented in struct vcpu_time_info should be sufficient to do the
> necessary mapping (or else I can't see what's different in your
> case from the usual PV or PVHVM one).
>
>> A solution would be to modify the runstate information mapped via
>> VCPUOP_register_runstate_memory_area: it could contain state_entry_time
>> rebased to the guests tsc.
>
> No, that one's defined to be matching up with vcpu_time_info's
> system_time.

Ah, okay. Then this was a mis-interpretation on my side.

Thanks for the info. :-)

I'll start another try based on this.


Juergen

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Juergen Gross                 Principal Developer Operating Systems
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