* Avi Kivity <[EMAIL PROTECTED]> wrote:
> >Is there no cheap way to do this flushing preemptively (say in
> >vcpu_put()), to make the VM context potentially loadable into another
> >CPU?
>
> You could issue a vmclear, but that forces a vm entry on the _same_
> cpu to use vmlaunch instead of vmresume, which is documented as
> expensive.
hm. Could you try to just do a vmresume nevertheless - maybe it works
but is undocumented? What would be nice is a 'vmflush' instruction that
still keeps the state usable.
> It is expected that, in general, VMRESUME will have lower latency than
> VMLAUNCH. Since “migrating” a VMCS from one logical processor to
> another requires use of VMCLEAR (see Section 20.10.1), which sets the
> launch state of the VMCS to “clear,” such migration requires the next
> VM entry to be performed using VMLAUNCH. Software developers can avoid
> the performance cost of increased VM-entry latency by avoiding
> unnecessary migration of a VMCS from one logical processor to another.
doh, very helpful ...
Ingo
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