linux-kernel - Re: RCU treating guest mode just like it does user-mode execution

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Message-ID: <20110818004459.GQ2419@linux.vnet.ibm.com>
Date:	Wed, 17 Aug 2011 17:44:59 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Gleb Natapov <gleb@...hat.com>, linux-kernel@...r.kernel.org,
	mtosatti@...hat.com, kvm@...r.kernel.org
Subject: Re: RCU treating guest mode just like it does user-mode execution

On Wed, Aug 17, 2011 at 05:28:46PM -0700, Avi Kivity wrote:
> On 08/17/2011 05:25 PM, Paul E. McKenney wrote:
> >>  >
> >>  Wouldn't scheduling-clock interrupt kick vcpu out of a guest mode much
> >>  earlier then 30 seconds?
> >
> >The scheduling-clock interrupt would happen, but I do not know whether
> >or not it would kick the vcpu out of guest mode in such a way that
> >would result in RCU thinking that the CPU has passed through a quiescent
> >state.
> >
> 
> The result can only be one of
> 
>   reenter guest (and rcu_virt_note_context_switch)
>   schedule()
>   exit to userspace

Very good, thank you both for bearing with me on this!

							Thanx, Paul
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