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From jharshman <>
Subject [GitHub] cloudstack pull request: CLOUDSTACK-9004: Add features to HyperVEn...
Date Fri, 30 Oct 2015 23:48:22 GMT
Github user jharshman commented on the pull request:
    My apologies Daan,
    I am happy to clarify.
    The PR for this Jira ticket (9004), was created as a subtask of CLOUDSTACK-8978.  It's
intent is to add the ability to set certain hv parameters with an end goal in 8978 of implementing
hyper-V enlightenment features for Windows Server 2008 guests.
    The current code for HyperVEnlightenmentFeatureDef only allowed the setting of the hv_relaxed
bit.  This bit disables a windows sanity check that commonly results in a BSOD when the VM
is running on a host under heavy load.
    The change here adds the ability to set the hv_vapic and hv_spinlocks bits as well as
retry time.  The hv_vapic bit tries to reduce interrupt overhead in guests.  The hv_spinlock
bit is used by the guest to notify the hypervisor that the calling virtual processor is attempting
to access a resource that may be held by another virtual processor.  For the host, the retry
value for hv_spinlock indicates the number of times the virtual processor should attempt to
access before the spinlock is considered excessive.
    Basically these changes are setting the stage for changes I am going to submit in CLOUDSTACK-8974.

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