Message-ID: <4AE07541.8060903@redhat.com>
Date: Thu, 22 Oct 2009 17:07:45 +0200
From: Avi Kivity <avi@redhat.com>
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To: Gregory Haskins <gregory.haskins@gmail.com>
CC: Gleb Natapov <gleb@redhat.com>, Gregory Haskins <ghaskins@novell.com>,
       kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
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Subject: Re: [KVM PATCH 1/2] KVM: Directly inject interrupts via irqfd
References: <20091021143042.14955.22470.stgit@dev.haskins.net> <20091021143453.14955.80578.stgit@dev.haskins.net> <20091021152621.GR29477@redhat.com> <4ADF2A1B.3010205@gmail.com> <20091021153640.GS29477@redhat.com> <4ADF2BDD.40706@gmail.com>
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On 10/21/2009 05:42 PM, Gregory Haskins wrote:
> I believe Avi, Michael, et. al. were in agreement with me on that design
> choice.  I believe the reason is that there is no good way to do EOI/ACK
> feedback within the constraints of an eventfd pipe which would be
> required for the legacy pin-type interrupts.  Therefore, we won't even
> bother trying.  High-performance subsystems will use irqfd/msi, and
> legacy emulation can use the existing injection code (which includes the
> necessary feedback for ack/eoi).
>
>    

Right.  But we don't actually prevent anyone using non-msi with irqfd, 
which can trigger the bad lock usage from irq context, with a nice boom 
afterwards.  So we need to either prevent it during registration, or to 
gracefully handle it afterwards.

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

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