[Xen-devel] emulated tsc and frequency info

To:	"xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject:	[Xen-devel] emulated tsc and frequency info
From:	Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
Date:	Tue, 20 Jul 2010 11:20:37 +0200
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Hi,

with xen 4.0 and xen-unstable I see weird tsc information in my HVM-domain
with PV-driver, if xen chooses to emulate tsc (d->arch.vtsc is set):

In the shared info page the tsc_to_system_mul is still reflecting the host
cpu frequency instead of the emulated 1 GHz.

The reason is quite simple: tsc_set_info() is never called with a gtsc_khz
value other than 0. I wonder which solution is the correct one:
- if tsc_set_info() is called with gtsc_khz=0, assume 1 GHz (my favorite).
- don't use 0 as default value for gtsc_khz when calling tsc_set_info()
  (this would require changes in the tools, too).
- let the domU check the vtsc-flag in cpuid-info and assume 1 GHz then (very
  ugly in my opinion).

Any thoughts?


Juergen

--
Juergen Gross                 Principal Developer Operating Systems
TSP ES&S SWE OS6                       Telephone: +49 (0) 89 3222 2967
Fujitsu Technology Solutions              e-mail: juergen.gross@xxxxxxxxxxxxxx
Domagkstr. 28                           Internet: ts.fujitsu.com
D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html

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[Xen-devel] emulated tsc and frequency info