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[Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts
From: |
Alexander Graf |
Subject: |
[Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts |
Date: |
Mon, 17 Jan 2011 17:33:31 +0100 |
User-agent: |
Thunderbird 2.0.0.23 (X11/20090817) |
Jan Kiszka wrote:
> On 2011-01-17 17:04, Alexander Graf wrote:
>
>> 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?
>>
>>
>
> Worse might also be that unknown issue that force you to inject an IRQ
> here. We don't know. That's probably worst.
>
Well, IIRC the issue was that usually a level high interrupt line would
simply retrigger an interrupt after enabling the interrupt line in the
APIC again. Unless my memory completely fails on me, that didn't happen,
so I added the manual retrigger on a partial command ACK in ahci code.
Alex
- [Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts, Jan Kiszka, 2011/01/17
- [Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts, Alexander Graf, 2011/01/17
- [Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts, Jan Kiszka, 2011/01/17
- [Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts, Gerd Hoffmann, 2011/01/18
- [Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts, Alexander Graf, 2011/01/18
- [Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts, Jan Kiszka, 2011/01/18
- Re: [Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts, Aurelien Jarno, 2011/01/22
- Re: [Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts, Edgar E. Iglesias, 2011/01/22
- Re: [Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts, Alexander Graf, 2011/01/22
- Re: [Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts, Aurelien Jarno, 2011/01/22
- Re: [Qemu-devel] Re: [PATCH 8/8] ahci: fix !msi interrupts, Edgar E. Iglesias, 2011/01/22