Xen devel - Dec 2008 - Question about time measure in Guest Windows

Hi:
 
I intend to use RDTSC to make some time tests in Xen guest WinXP. However, from
Intel Developer''s Manual I noticed that RDTSC will cause VMExit if
"RETSC exiting" VM-Execution control field is 1. So I wonder: How to
query VM-Execution control field in a programmable way?
 
BTW: On Intel Developer''s Manual, it mentioned a method using
IA32_VMX_PROCBASED_CTLS MSR, but this is just to report which bits can be set on
processor-based VM-EXECUTION controls, rather than telling you the content of
this structure.
 
Thanks!
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Thanks for your suggest! 
 
But I have a further question about this issue: In my tests, I need to use some
other instructions like RDTSC that may cause VMExit conditionally, one example
is WBINVD which is another bit in VM-execution control field. From your advice,
can I say that I can ignore all the bits of VM-execution control field in Xen?
Otherwise, How to query VM-Execution control field in a programmable way?
Thanks!
Nanxuan> Date: Thu, 4 Dec 2008 07:10:36 -0800> From:
dan.magenheimer@oracle.com> To: nanxuan_xu@live.cn> Subject: RE:
[Xen-devel] Question about time measure in Guest Windows> > "RDTSC
exiting VM execution control field" is available so that> a hypervisor
can trap ALL guest uses of the RDTSC instruction.> Xen does not currently use
this, so you can use RDTSC in a Xen> Windows guest without worrying about
it.> > HOWEVER, be aware that on many SMP machines, the TSC is not>
synchronized between processors and your guest may move between> processors
without its knowledge. So two consecutive reads> of TSC by a guest may appear
as if TSC is going backwards or> jumps forward by many many ticks.> >
-----Original Message-----> From: XuNanxuan [mailto:nanxuan_xu@live.cn]>
Sent: Wednesday, December 03, 2008 11:45 PM> To:
xen-devel@lists.xensource.com> Subject: [Xen-devel] Question about time
measure in Guest Windows> > > Hi:> > I intend to use RDTSC to
make some time tests in Xen guest
 WinXP. However, from Intel Developer''s Manual I noticed that RDTSC
will cause VMExit if "RETSC exiting" VM-Execution control field is 1.
So I wonder: How to query VM-Execution control field in a programmable way?>
> BTW: On Intel Developer''s Manual, it mentioned a method using
IA32_VMX_PROCBASED_CTLS MSR, but this is just to report which bits can be set on
processor-based VM-EXECUTION controls, rather than telling you the content of
this structure.> > Thanks!
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