linux-kernel - Re: [PATCH v10 2/2] kvm: Add resampling irqfds for level triggered interrupts

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Message-ID: <20120919090845.GA26517@redhat.com>
Date:	Wed, 19 Sep 2012 12:08:45 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Alex Williamson <alex.williamson@...hat.com>, gleb@...hat.com,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 2/2] kvm: Add resampling irqfds for level triggered
 interrupts

On Wed, Sep 19, 2012 at 11:59:33AM +0300, Avi Kivity wrote:
> > @@ -247,9 +383,36 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
> >  		/* This fd is used for another irq already. */
> >  		ret = -EBUSY;
> >  		spin_unlock_irq(&kvm->irqfds.lock);
> > +		mutex_unlock(&kvm->irq_lock);
> >  		goto fail;
> >  	}
> >  
> > +	if (resampler) {
> > +		struct _irqfd_resampler *resampler_tmp;
> > +
> > +		/*
> > +		 * Re-use a resampler if it's already registered on the
> > +		 * gsi we need.  Free the one we created above if found,
> > +		 * otherwise add to the list and setup the irq ack notifier.
> > +		 */
> > +		list_for_each_entry(resampler_tmp,
> > +				    &kvm->irqfds.resamplers, list) {
> > +			if (resampler_tmp->notifier.gsi == irqfd->gsi) {
> > +				irqfd->resampler = resampler_tmp;
> > +				break;
> > +			}
> > +		}
> > +
> > +		if (irqfd->resampler == resampler) {
> > +			list_add(&resampler->list, &kvm->irqfds.resamplers);
> > +			__kvm_register_irq_ack_notifier(kvm,
> > +							&resampler->notifier);
> > +		} else
> > +			kfree(resampler);
> > +
> > +		list_add_rcu(&irqfd->resampler_list, &irqfd->resampler->irqfds);
> > +	}
> > +
> 
> Whoa.  Can't we put the resampler entry somewhere we don't need to
> search for it?  Like a kvm_kernel_irq_routing_entry, that's indexed by
> gsi already (kvm_irq_routing_table::rt_entries[gsi]).

I'm not sure why would we bother optimizing this,
but if we do, I guess we could look for the irq notifier
which is already indexed by gsi.


> 
> 
> -- 
> error compiling committee.c: too many arguments to function
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