On Wed, Jul 06, 2016 at 12:44:58PM +0200, Paolo Bonzini wrote:

quoted

Paolo, could you help out with an (x86) KVM interface for this?

If it's just for spin loops, you can check if the version field in the
steal time structure has changed.

That would require remembering the old value, no?

That would work with a previous interface proposal, see:

  http://lkml.kernel.org/r/1466937715-6683-2-git-send-email-xinhui.pan@linux.vnet.ibm.com

the vcpu_get_yield_count() thing would match that I think.

However the current proposal:

  http://lkml.kernel.org/r/1467124991-13164-2-git-send-email-xinhui.pan@linux.vnet.ibm.com

dropped that in favour of only vcpu_is_preempted(), which requires being
able to tell if a (remote) vcpu is currently running or not, which iirc,
isn't possible with the steal time sequence count.