Re: [Xen-devel] [RFC] Hypervisor RNG and enumeration

[Jake Oshins <jakeo@xxxxxxxxxxxxx>]

>I have no objection to specifying that these reads may be quite slow.
>Guests should only use them at boot and if they have some reason to
>distrust their RNG pool.

>The latter can legitimately happen after various types of suspend or
>after migration (detected by VM Generation ID, for example).

Just as a point of clarification, the VM Generation ID changes (at least in the 
Hyper-V implementation) only when the VM may have observed a different future, 
as when a VM backup is restored, a checkpoint is applied, etc.  It does not 
change during migration, when the VM is suspended or when it is rebooted.  I've 
heard anecdotes from application vendors saying that there is some other 
hypervisor that actually does change the ID at these moments and they wanted us 
to us to fix that, until I explained that I only control Hyper-V.

-- Jake Oshins

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