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

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Message-ID: <4E4C5CBE.5040102@redhat.com>
Date:	Wed, 17 Aug 2011 17:28:46 -0700
From:	Avi Kivity <avi@...hat.com>
To:	paulmck@...ux.vnet.ibm.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 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

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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