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Re: [Xen-devel] using mapped vcpu_runstate_info in hvm guest

  • To: Jan Beulich <JBeulich@xxxxxxxx>
  • From: Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
  • Date: Wed, 20 Nov 2013 14:29:55 +0100
  • Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Wed, 20 Nov 2013 13:30:11 +0000
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On 20.11.2013 14:07, Jan Beulich wrote:
On 13.11.13 at 14:50, Juergen Gross <juergen.gross@xxxxxxxxxxxxxx> 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

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

Thanks for the info. :-)

I'll start another try based on this.


Juergen Gross                 Principal Developer Operating Systems
PBG PDG ES&S SWE OS6                   Telephone: +49 (0) 89 62060 2932
Fujitsu                                   e-mail: juergen.gross@xxxxxxxxxxxxxx
Mies-van-der-Rohe-Str. 8                Internet: ts.fujitsu.com
D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html

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