Re: [Xen-devel] [PATCH 0/2] Viridian MSRs

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 05 November 2013 15:16
> To: Paul Durrant
> Cc: Andrew Cooper; xen-devel; Keir (Xen.org)
> Subject: Re: [PATCH 0/2] Viridian MSRs
> 
> >>> On 15.10.13 at 20:12, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> wrote:
> > This set of two patches advertises 3 constant, read-only MSRs of timing
> > information to a viridian capable VM.
> >
> > There is an as-yet-unidentified issue when running Windows 8.1 / Server
> 2012r2
> > under Xen where it will periodically (1 in 10 attempt) appear to fall into
> > an
> > idle loop rather than schedule userspace processes (such as failing to run a
> > login session).
> >
> > I am still investigating the underlying cause.  One possibility is an
> > interaction of TSC time calibration interacting poorly with the Xen
> > scheduler.
> >
> > Unfortunately, attempting to divine what windows is unhappy about with
> its
> > environment is rather tricky (even a BSOD would be more useful than the
> > current symptoms), but providing these MSRs causes Windows to prefer
> rdtsc
> > over the HPET main counter as a source of time, and 'fixes' the above issue.
> >
> > CC: Paul Durrant <paul.durrant@xxxxxxxxxx>
> 
> I was kind of expecting to get a Reviewed-by (or other comments)
> from you on this - is there any hope for this to be happening at
> some point?
> 

Since I originated the code and both patches carry my s-o-b I didn't feel it 
was appropriate for me to review or ack.

  Paul

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