OK.
Signed-off-by: Li Zhang <li.zhang@xxxxxxxxx>
Thanks
> -----Original Message-----
> From: Dan Magenheimer [mailto:dan.magenheimer@xxxxxxxxxx]
> Sent: Thursday, July 10, 2008 5:33 AM
> To: dan.magenheimer@xxxxxxxxxx; Zhang, Li; Xen-Devel (E-mail)
> Cc: Tian, Kevin
> Subject: [PATCH] softtsc (was RE: [Xen-devel] Guest TSC and Xen (Intel and
> AMD feedback please))
>
> The attached patch adds a new Xen boot option "softtsc" that
> causes all hvm domains to trap and emulate all rdtsc instructions
> and fetch Xen system time instead of the hardware tsc. As
> a result, the processor will appear to be running at 1000.xyz MHz
> (where xyz indicates some fraction that seems to vary slightly
> across different boots). I've also added a line of output to
> "xm debug-key t" to report softsc and tsc-related CPU features.
>
> (Keir, though 3.3 functionality freeze is past, this is more of a
> diagnostic aid and defaults off, so I don't know if you would
> consider it for 3.3.)
>
> Signed-off-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
>
> Dan
>
> P.S. Thanks to Li Zhang for coding the foundation for this patch.
> Li, do you want to provide a signed-off-by line too?
>
> > -----Original Message-----
> > From: Dan Magenheimer [mailto:dan.magenheimer@xxxxxxxxxx]
> > Sent: Tuesday, July 08, 2008 6:30 PM
> > To: 'Zhang, Li'; 'Xen-Devel (E-mail)'
> > Cc: 'Tian, Kevin'
> > Subject: RE: [Xen-devel] Guest TSC and Xen (Intel and AMD
> > feedback please)
> >
> >
> > Looks great! I am continuing to code and test. Some
> > preliminary results:
> >
> > 1) Substituting hvm_get_guest_time() for hvm_get_guest_tsc()
> > seems to just work! The hvm
> > guest believes it is running on a 1000.185 MHz clock.
> >
> > 2) On my test box, a guest rdtsc without softtsc takes about
> > 30ns. With softtsc,
> > rdtsc takes about 1us.
> >
> > 3) On my user-land test program, I am seeing rare "Time goes
> > backwards", even with
> > hvm_get_guest_time(). I'm trying to track this down.
> >
> > Dan
> >
> > > -----Original Message-----
> > > From: Zhang, Li [mailto:li.zhang@xxxxxxxxx]
> > > Sent: Tuesday, July 08, 2008 3:47 AM
> > > To: Zhang, Li; 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
> > > 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
> > > > > > >
> > > >
> > > > _______________________________________________
> > > > Xen-devel mailing list
> > > > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > > > http://lists.xensource.com/xen-devel
> > >
> > >
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