From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [PATCH RFC] kvm: deliver msix interrupts from irq handler
Date: Thu, 19 Jan 2012 18:39:17 +0200
Message-ID: <20120119163917.GB18770@redhat.com>
References: <20120118181023.GA4140@redhat.com>
 <20120119072123.GE9571@redhat.com>
 <20120119134957.GC4009@redhat.com>
 <20120119150217.GA20920@redhat.com>
 <20120119155748.GA6340@redhat.com>
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Cc: Alex Williamson <alex.williamson@redhat.com>,
	jan.kiszka@siemens.com, Avi Kivity <avi@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org
To: "Michael S. Tsirkin" <mst@redhat.com>
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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.