Re: pv clock: kvm is incompatible with xen :-(

[Gerd Hoffmann <kraxel@redhat.com>]

Jeremy Fitzhardinge wrote:
> Xen could change the parameters in the instant after get_time_values(). 
> That change could be as a result of suspend-resume, so the parameters
> and the tsc could be wildly different.

Ah, ok, forgot the rdtsc in the picture.  With that in mind I fully
agree that the loop is needed.  I think kvm guests can even hit that one
with the vcpu migrating to a different physical cpu, so we better handle
it correctly ;)

> Sure, but get_time_values() has several other callers.

Not really.  There are only two calls, one in clocksource_read() and one
in the init path.  The later is superfluous I think because
clocksource_read() is the only user of the shadowed time info.

cheers,
  Gerd

-- 
http://kraxel.fedorapeople.org/xenner/

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