RE: [Xen-devel] Guest TSC and Xen (Intel and AMD feedback please)

["Zhang, Li" <li.zhang@xxxxxxxxx>]

Hi, Dan
Please ignore previous comments. The above attachment is OK. Sorry for that. :(

>  -----Original Message-----
>  From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
>  [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Zhang, Li
>  Sent: Tuesday, July 08, 2008 2:58 PM
>  To: dan.magenheimer@xxxxxxxxxx; Xen-Devel (E-mail)
>  Cc: Tian, Kevin
>  Subject: RE: [Xen-devel] Guest TSC and Xen (Intel and AMD feedback please)
>  
>  In fact, the issue is from guest. In the guest's terminal, it shows that 
> "your
>  time source seems to be instable..."
>  
>  >  -----Original Message-----
>  >  From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
>  >  [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Zhang, Li
>  >  Sent: Tuesday, July 08, 2008 2:49 PM
>  >  To: dan.magenheimer@xxxxxxxxxx; Xen-Devel (E-mail)
>  >  Cc: Tian, Kevin
>  >  Subject: RE: [Xen-devel] Guest TSC and Xen (Intel and AMD feedback please)
>  >
>  >  Hi, Dan
>  >
>  >  This is the patch which I think it has been completed VT. But there is an
>  >  instable issue. The reason may be from that this interception is not bound
>  >  to timer mode yet.
>  >
>  >  Thanks
>  >  --Li
>  >
>  >  >  -----Original Message-----
>  >  >  From: Dan Magenheimer [mailto:dan.magenheimer@xxxxxxxxxx]
>  >  >  Sent: Tuesday, July 08, 2008 11:34 AM
>  >  >  To: Zhang, Li; Xen-Devel (E-mail)
>  >  >  Cc: Tian, Kevin; dan.magenheimer@xxxxxxxxxx
>  >  >  Subject: RE: [Xen-devel] Guest TSC and Xen (Intel and AMD feedback
>  please)
>  >  >
>  >  >  Thanks Kevin and Li --
>  >  >
>  >  >  A couple of questions:
>  >  >
>  >  >  1) If the EXITING flag to be set in vmcs.c is to be controlled by a xen
>  >  boot
>  >  >  option, would this work:
>  >  >
>  >  >  static int opt_softtsc = 0;
>  >  >  boolean_param("softtsc", opt_softtsc);
>  >  >    :
>  >  >  min = /* original code */
>  >  >  if (opt_softtsc) min |= CPU_BASED_RDTSC_EXITING;
>  >  >
>  >  >  2) In vmx_rdtsc_intercept(/* need regs as param*/) if we change the
>  >  >  rdtscll(tsc) to be tmptsc = hvm_get_guest_tsc() and then set regs->edx
>  amd
>  >  >  regs->eax from tmptsc, are we almost done?
>  >  >
>  >  >  3) Des Linux or Windows use the CR4.TSD flag and, if so, what code gets
>  >  called
>  >  >  to force the trap?
>  >  >
>  >  >  4) Does Linux or Windows use RDMSR/WRMSR of tsc?  Is there already code
>  >  >  somewhere to emulate WRMSR of tsc?
>  >  >
>  >  >  Sorry I am not very familar with the details of the ia32 instruction
>  set.
>  >  >
>  >  >  Thanks,
>  >  >  Dan
>  >  >
>  >  >  > -----Original Message-----
>  >  >  > From: Zhang, Li [mailto:li.zhang@xxxxxxxxx]
>  >  >  > Sent: Monday, July 07, 2008 9:00 PM
>  >  >  > To: dan.magenheimer@xxxxxxxxxx; Xen-Devel (E-mail)
>  >  >  > Cc: Tian, Kevin
>  >  >  > Subject: RE: [Xen-devel] Guest TSC and Xen (Intel and AMD
>  >  >  > feedback please)
>  >  >  >
>  >  >  >
>  >  >  > Hi, Dan
>  >  >  > This seems not to be enough. I will cook another patch.
>  >  >  >
>  >  >  > >  -----Original Message-----
>  >  >  > >  From: Zhang, Li
>  >  >  > >  Sent: Tuesday, July 08, 2008 10:28 AM
>  >  >  > >  To: Tian, Kevin; 'dan.magenheimer@xxxxxxxxxx'; 'Xen-Devel
>  (E-mail)'
>  >  >  > >  Subject: RE: [Xen-devel] Guest TSC and Xen (Intel and AMD
>  >  >  > feedback please)
>  >  >  > >
>  >  >  > >  Hi, Dan
>  >  >  > >
>  >  >  > >  I just add some code to produce vmexit. The function
>  >  >  > vmx_rdtsc_intercept()
>  >  >  > >  is not completed. It is needed to add some code to get the
>  >  >  > guest tsc.
>  >  >  > >
>  >  >  > >  Thanks
>  >  >  > >  --Li
>  >  >  > >
>  >  >  > >  >  -----Original Message-----
>  >  >  > >  >  From: Tian, Kevin
>  >  >  > >  >  Sent: Tuesday, July 08, 2008 9:39 AM
>  >  >  > >  >  To: 'dan.magenheimer@xxxxxxxxxx'; Xen-Devel (E-mail)
>  >  >  > >  >  Cc: Zhang, Li
>  >  >  > >  >  Subject: RE: [Xen-devel] Guest TSC and Xen (Intel and
>  >  >  > AMD feedback please)
>  >  >  > >  >
>  >  >  > >  >  >From: Dan Magenheimer [mailto:dan.magenheimer@xxxxxxxxxx]
>  >  >  > >  >  >Sent: 2008年7月5日 1:32
>  >  >  > >  >  >
>  >  >  > >  >  >> >Is this something that you (or Intel in general)
>  >  >  > could look at?
>  >  >  > >  >  >> >I would be happy to participate but I don't think I
>  >  >  > understand
>  >  >  > >  >  >> >VT well enough.  Once the trap occurs, I suppose
>  >  >  > Xen system time
>  >  >  > >  >  >> >could be used as the virtual TSC, possibly scaled up.
>  >  >  > >  >  >> >
>  >  >  > >  >  >>
>  >  >  > >  >  >> There should be tiny related to VT, as only turning
>  >  >  > on some bit to
>  >  >  > >  >  >> allow RDTSC trapping and then the rest stuff should be 
> common
>  >  >  > >  >  >> how to handle it. We'll take a look, but can't
>  >  >  > commit the time due
>  >  >  > >  >  >> to other scheduled bandwidth. But if you'd like to
>  >  >  > jump in early
>  >  >  > >  >  >> we definitely can help with VT side.
>  >  >  > >  >  >
>  >  >  > >  >  >If you can post a patch with code that:
>  >  >  > >  >  >
>  >  >  > >  >  >1) declares a boolean global variable: softtsc = 0
>  >  >  > >  >  >2) if the variable is set, a rdtsc instruction in any hvm
>  >  >  > >  >  >   domain causes a trap
>  >  >  > >  >  >3) the trap handler just does a physical rdtsc and returns
>  >  >  > >  >  >
>  >  >  > >  >  >then I could probably take it from there.
>  >  >  > >  >
>  >  >  > >  >  OK, and Li in CC will take a look and bake a patch for you.
>  >  >  > >  >
>  >  >  > >  >  Thanks,
>  >  >  > >  >  Kevin
>  >  >  >
>  
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Attachment: tsc.patch
Description: tsc.patch

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