linux-kernel - Re: [PATCH RFC] kvm: enable irq injection from interrupt context

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Message-ID: <4C921823.5080602@redhat.com>
Date:	Thu, 16 Sep 2010 15:14:11 +0200
From:	Avi Kivity <avi@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	Gleb Natapov <gleb@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] kvm: enable irq injection from interrupt context

  On 09/16/2010 02:57 PM, Michael S. Tsirkin wrote:
> >
> >  >  >  If you want to split parts that asserts irq and de-asserts it then we
> >  >  >  should have irqfd that tracks line status and knows interrupt line
> >  >  >  polarity.
> >  >
> >  >  Yes, it can know about polarity even though I think it's cleaner to do this
> >  >  per gsi. But it can not track line status as line is shared with
> >  >  other devices.
> >  It should track only device's line status.
>
> There is no such thing as device's line status on real hardware, either.
> Devices do not drive INT# high: they drive it low (all the time)
> or do not drive it at all.
>

That's just an implementation detail.  Devices either assert INT# or 
they do not.  Tying the wires together constitutes an AND gate.  This 
gate has to be modelled somewhere, currently it's in qemu's pci emulation.

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

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