Re: [kvm-ppc-devel] [PATCH 2 of 2] Add PowerPC KVM guest

[Jerone Young <jyoung5@us.ibm.com>]

On Wed, 2008-04-02 at 11:17 +0200, Christian Ehrhardt wrote:
> Jerone Young wrote:
> > Add PowerPC KVM guest wait handling support
> > 
> > This patch handles a guest that is in a wait state. This ensures that the guest is not allways eating up 100% cpu when it is idle.
> > 
> > Signed-off-by: Jerone Young <jyoung5@us.ibm.com>
> > 
> > diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> > --- a/arch/powerpc/kvm/powerpc.c
> > +++ b/arch/powerpc/kvm/powerpc.c
> > @@ -164,13 +164,12 @@ void kvmppc_dump_vcpu(struct kvm_vcpu *v
> [...]
> 
> > +	/* handle guest vcpu that is in wait state */
> > +	/* XXX eventually replace with kvm_vcpu_block() */
> > +	if (vcpu->arch.msr & MSR_WE) {
> 
> ###
> > +		DECLARE_WAITQUEUE(wait, current);
> > +
> > +		add_wait_queue(&vcpu->wq, &wait);
> > +
> > +		while (!kvm_cpu_has_interrupt(vcpu)
> > +			&& !signal_pending(current)
> > +			&& !kvm_arch_vcpu_runnable(vcpu)) {
> > +			
> > +			set_current_state(TASK_INTERRUPTIBLE);
> > +			schedule();
> > +		}
> > +		
> > +		__set_current_state(TASK_RUNNING);
> > +		remove_wait_queue(&vcpu->wq, &wait);
> ###
> 
> We talked about calling kvm_vcpu_block here which does the same. What has become of it?
> I mean the check is the same now and the waitqueues too. The only difference is vcpu_load/put which calls kvm_arch_vcpu_load/put which are noops for us.
> I the issues are only caused by the prempt/lockign stuff there - ?is it? - this could either changed there in kvm_vcpu_block e.g. with a ifdef, a runtime if or by moving that to the architectures which support these stuff.
> 

The reason for not using kvm_vcpu_block is that I couldn't figure out in
enough time how to get the premempt notify stuff to work. We really
don't even need it, but it's used in kvm_vcpu_block and I just don't
have the time to figure out what all is needed for it to work.

> > +	}
> > 
> >  	/* Do some exit accounting. */
> 
> 


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