From: Avi Kivity <avi@redhat.com>
To: Alexander Graf <agraf@suse.de>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
qemu-devel List <qemu-devel@nongnu.org>
Subject: [Qemu-devel] Re: [RFC] KVM: PPC: Add level based interrupt logic
Date: Wed, 01 Sep 2010 14:56:53 +0300 [thread overview]
Message-ID: <4C7E3F85.8090201@redhat.com> (raw)
In-Reply-To: <B1E5FE68-76C8-4083-8EA0-3D9762435084@suse.de>
On 09/01/2010 02:47 PM, Alexander Graf wrote:
> On 01.09.2010, at 13:45, Avi Kivity wrote:
>
>> On 09/01/2010 12:38 PM, Alexander Graf wrote:
>>> On 01.09.2010, at 09:41, Avi Kivity wrote:
>>>
>>>> On 08/31/2010 01:07 PM, Alexander Graf wrote:
>>>>> KVM on PowerPC used to have completely broken interrupt logic. Usually,
>>>>> interrupts work by having a PIC that pulls a line up/down, so the CPU knows
>>>>> that an interrupt is active. This line stays active until some action is
>>>>> done to the PIC to release the line.
>>>>>
>>>>> On KVM for PPC, we just checked if there was an interrupt pending and pulled
>>>>> a line in the kernel module. We never released it though, hoping that kernel
>>>>> space would just declare an interrupt as released when injected - which is
>>>>> wrong.
>>>>>
>>>>> To fix this, we need to completely redesign the interrupt injection logic.
>>>>> Whenever an interrupt line gets triggered, we need to notify kernel space
>>>>> that the line is up. Whenever it gets released, we do the same. This way
>>>>> we can assure that the interrupt state is always known to kernel space.
>>>>>
>>>>> This fixes random stalls in KVM guests on PowerPC that were waiting for
>>>>> an interrupt while everyone else thought they received it already.
>>>> This is more or less equivalent to KVM_IRQ_LINE.
>>> My question was if you think the internal C interface is generic enough or if it needs a lot more magic for x86 anyways :).
>>>
>> So you noticed I avoided it. Well, being forced to look, I don't think it's worthwhile to try to be generic here. Both the PIC<->APIC and the APIC<->core interfaces are too complicated to be modelled by a single line.
> Makes sense. Well, I guess it doesn't hurt to have the interface as is and only implement it for PPC for now.
>
>
Why not limit it to ppc? Someone might call it by accident.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
next prev parent reply other threads:[~2010-09-01 11:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-31 10:07 [Qemu-devel] [RFC] KVM: PPC: Add level based interrupt logic Alexander Graf
2010-09-01 7:41 ` [Qemu-devel] " Avi Kivity
2010-09-01 9:38 ` Alexander Graf
2010-09-01 11:45 ` Avi Kivity
2010-09-01 11:47 ` Alexander Graf
2010-09-01 11:56 ` Avi Kivity [this message]
2010-09-01 11:58 ` Alexander Graf
2010-09-01 12:09 ` Avi Kivity
2010-09-01 12:09 ` Avi Kivity
2010-09-01 12:10 ` Alexander Graf
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