Re: [PATCH RFC] kvm: deliver msix interrupts from irq handler

[Gleb Natapov <gleb@redhat.com>]

On Thu, Jan 19, 2012 at 05:57:48PM +0200, Michael S. Tsirkin wrote:
> On Thu, Jan 19, 2012 at 05:02:17PM +0200, Gleb Natapov wrote:
> > On Thu, Jan 19, 2012 at 03:49:57PM +0200, Michael S. Tsirkin wrote:
> > > > > +	irq_rt = rcu_dereference(kvm->irq_routing);
> > > > > +	if (irq < irq_rt->nr_rt_entries)
> > > > > +		hlist_for_each_entry(e, n, &irq_rt->map[irq], link) {
> > > > > +			if (ei->type == KVM_IRQ_ROUTING_MSI)
> > > > > +				ret = kvm_set_msi(e, kvm, irq_source_id, level,
> > > > > +						  host_irq);
> > > > > +			else
> > > > > +				ret = -EWOULDBLOCK;
> > > > > +			break;
> > > > > +		}
> > > > > +	rcu_read_unlock_bh();
> > > > > +	return ret;
> > > > > +}
> > > > > +
> > > > Share implementation with kvm_set_irq().
> > > 
> > > I considered this. There are several reasons not to do it:
> > > - Amount of common code is very small
> > Why? Just pass msi_only flag to kvm_set_irq() and skip an entry if flag is
> > set and entry type is not msi.
> > 
> > > - As it's separate, it's more obvious that it can't block (kvm_set_irq can block)
> > >   We can even tag kvm_set_irq with might_sleep.
> > They can still be two separate function calling common one.
> 
> No, the common code is the surrounding foreach loop,
> the internal if branch is different.
> 
I do not see any complication whatsoever. The reuse it trivial.

--
			Gleb.