From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pekka Enberg <penberg@kernel.org>
Subject: Re: [PATCH 1/3] kvm tools: Make virtio-net kvm__irq_line thread safe
Date: Fri, 29 Apr 2011 13:37:56 +0300
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Cc: Sasha Levin <levinsasha928@gmail.com>,
	Asias He <asias.hejun@gmail.com>, Ingo Molnar <mingo@elte.hu>,
	Prasad Joshi <prasadjoshi124@gmail.com>, kvm@vger.kernel.org
To: Cyrill Gorcunov <gorcunov@gmail.com>
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On Fri, Apr 29, 2011 at 1:02 PM, Cyrill Gorcunov <gorcunov@gmail.com> wrote:
> So, if I understand all the things correct -- making virtio devices to
> belong separated irqs
> issued some race conditions on read\write operations between host and
> guest and adding
> thread pool revealed it, right? (because previously we were doing all
> the work inside i/o
> path on guest site).

So does reverting commit a37089da817ce7aad9789aeb9fc09b68e088ad9a
("kvm tools: Use threadpool for virtio-net") fix things? I think the
problem here is that now RX path relies on VIRTIO_PCI_QUEUE_NOTIFY to
happen in order for it to trigger KVM_IRQ_LINE which is wrong. Using
shared IRQs obviously masks the problem which is why reverting
Cyrill's commit makes the problem go away.

                        Pekka