From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Gabriel L. Somlo" <gsomlo@gmail.com>
Subject: Re: RFC: ioapic polarity vs. qemu os-x guest
Date: Mon, 17 Feb 2014 13:01:37 -0500
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Cc: Alex Williamson <alex.williamson@redhat.com>,
	Alexander Graf <agraf@suse.de>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
	"eddie.dong@intel.com" <eddie.dong@intel.com>, pbonzini@redhat.com
To: "Michael S. Tsirkin" <mst@redhat.com>
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On Mon, Feb 17, 2014 at 12:57:00PM -0500, Gabriel L. Somlo wrote:
> On Sun, Feb 16, 2014 at 06:23:11PM +0200, Michael S. Tsirkin wrote:
> > Well there is a bigger issue: any interrupt with
> > multiple sources is broken.
> > 
> > __kvm_irq_line_state does a logical OR of all sources,
> > before XOR with polarity.
> > 
> > This makes no sense if polarity is active low.
> 
> So, do you think something like this would make sense, to address
> active-low polarity in __kvm_irq_line_state ?
> (this would be independent of the subsequent xor in
> kvm_ioapic_set_irq()):
 
Make that rather:

-static inline int __kvm_irq_line_state(unsigned long *irq_state,
+static inline int __kvm_irq_line_state(unsigned long *irq_state, int polarity,
					int irq_source_id, int level)
{
-        /* Logical OR for level trig interrupt */
	if (level)
		__set_bit(irq_source_id, irq_state);
	else
		__clear_bit(irq_source_id, irq_state);

-	return !!(*irq_state);
+	if (polarity) {
+		/* Logical AND for level trig interrupt, active-low */
+		return !~(*irq_state);
+	} else {
+		/* Logical OR for level trig interrupt, active-high */
+		return !!(*irq_state);
+	}
}

Thanks, and sorry for the noise :)
--Gabriel