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Date: Mon, 17 Jan 2011 17:04:48 +0100
From: Alexander Graf <agraf@suse.de>
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Subject: [Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts
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To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Joerg Roedel <Joerg.Roedel@amd.com>, Sebastian Herbszt <herbszt@gmx.de>, qemu-devel Developers <qemu-devel@nongnu.org>, Gerd Hoffmann <kraxel@redhat.com>

Jan Kiszka wrote:
> On 2011-01-17 17:00, Alexander Graf wrote:
>   
>> Jan Kiszka wrote:
>>     
>>> On 2010-12-20 22:13, Alexander Graf wrote:
>>>   
>>>       
>>>> When not using MSI, receiving an interrupt while the interrupt line is active
>>>> pulses the interrupt line. Without this, guests don't realize that a new
>>>> interrupt occured.
>>>>     
>>>>         
>>> This doesn't look OK. The device model should look at the currently used
>>> mode and switch between edge and level triggering accordingly. As it
>>> appears like this is what it already does, this change may just paper
>>> over the real issue.
>>>   
>>>       
>> Well, I have this internal abstraction to make edge and level triggered
>> interrupt triggering easier. irq_lower is a simple nop for the edge case.
>>
>>     
>
> I'm concerned about the artificial edge you generate for the level
> triggered case. That's not like real hw behaves. If you need it,
> something else might still be broken.
>   

Hrm. So worst case we generate a spurious interrupt?


Alex