From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1M77DI-0005DH-Sy
	for qemu-devel@nongnu.org; Thu, 21 May 2009 08:17:32 -0400
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1M77DD-0005BL-Vf
	for qemu-devel@nongnu.org; Thu, 21 May 2009 08:17:32 -0400
Received: from [199.232.76.173] (port=45718 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1M77DD-0005BI-T6
	for qemu-devel@nongnu.org; Thu, 21 May 2009 08:17:27 -0400
Received: from mx2.redhat.com ([66.187.237.31]:51785)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <mst@redhat.com>) id 1M77DD-0001FT-Ek
	for qemu-devel@nongnu.org; Thu, 21 May 2009 08:17:27 -0400
Date: Thu, 21 May 2009 15:14:24 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] [PATCH] qemu: msi irq allocation api
Message-ID: <20090521121424.GD25309@redhat.com>
References: <20090520162130.GA22109@redhat.com>
	<200905211134.21184.paul@codesourcery.com>
	<4A15346C.8090906@redhat.com>
	<200905211301.52089.paul@codesourcery.com>
	<4A154432.1060808@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <4A154432.1060808@redhat.com>
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Avi Kivity <avi@redhat.com>
Cc: Carsten Otte <cotte@de.ibm.com>, kvm@vger.kernel.org, Rusty Russell <rusty@rustcorp.com.au>, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, Christian Borntraeger <borntraeger@de.ibm.com>, Paul Brook <paul@codesourcery.com>

On Thu, May 21, 2009 at 03:08:18PM +0300, Avi Kivity wrote:
> Paul Brook wrote:
>>>>> In any case we need some internal API for this, and qemu_irq looks like
>>>>> a good choice.
>>>>>         
>>>> What do you expect to be using this API?
>>>>       
>>> virtio, emulated devices capable of supporting MSI (e1000?), device
>>> assignment (not yet in qemu.git).
>>>     
>>
>> It probably makes sense to have common infrastructure in pci.c to  
>> expose/implement device side MSI functionality. However I see no need 
>> for a direct API between the device and the APIC. We already have an 
>> API for memory accesses and MMIO regions. I'm pretty sure a system 
>> could implement MSI by pointing the device at system ram, and having 
>> the CPU periodically poll that.
>>   
>
> Instead of writing directly, let's abstract it behind a qemu_set_irq().   
> This is easier for device authors.  The default implementation of the  
> irq callback could write to apic memory, while for kvm we can directly  
> trigger the interrupt via the kvm APIs.

Right.

-- 
MST