Subject: Re: [PATCH 24/30] KVM: PPC: booke: call resched after every exit

From: Scott Wood <[email-masked]>
Date: Mon, 20 Feb 2012 11:18:41 -0600

On 02/20/2012 07:17 AM, Alexander Graf wrote:
> 
> On 18.02.2012, at 00:00, Scott Wood wrote:
> 
>> It would be simpler (both here and in the idle hcall) if we could just
>> drop support for CONFIG_PREEMPT=n. :-P
> 
> When running with CONFIG_PREEMPT=n we don't have to worry about interrupts being enabled though,

That's exactly when we *do* need to worry.  Interrupts can cause the
"need resched" condition to become true.

> since we only preempt on known good checkpoints, right?

Yes, and "entering the guest" is supposed to be one of those known good
checkpoints, similar to returning to userspace.  If we miss a reschedule
here, we're may not have another chance until the next timer interrupt.
 The code for returning to userspace is similarly structured.

-Scott