Re: [PATCH v2 0/4] implement vcpu preempted check

[Peter Zijlstra]

On Thu, Jul 07, 2016 at 11:42:15AM +0200, Peter Zijlstra wrote:
> I suspect you want something like so; except this has holes in.
> 
> We clear KVM_ST_PAD_PREEMPT before disabling preemption and we set it
> after enabling it, this means that if we get preempted in between, the
> vcpu is reported as running even though it very much is not.
> 
> Fixing that requires much larger surgery.

Note that this same hole is already a 'problem' for steal time
accounting. The thread can accrue further delays (iow steal time) after
we've called record_steal_time(). These delays will go unaccounted.