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Date: Wed, 14 May 2014 14:30:26 +0200
From: Stefan Hajnoczi <stefanha@gmail.com>
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Subject: Re: [Qemu-devel] [PATCH] e1000/rtl8139: forbid dealing with packets
 when VM is paused
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To: Zhanghailiang <zhang.zhanghailiang@huawei.com>
Cc: Zhouxiangjiu <zhouxiangjiu@huawei.com>, Peter Maydell <peter.maydell@linaro.org>, Peter Crosthwaite <peter.crosthwaite@xilinx.com>, "Michael S. Tsirkin" <mst@redhat.com>, Juan Quintela <quintela@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>, "Huangpeng (Peter)" <peter.huangpeng@huawei.com>, Alex Williamson <alex.williamson@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, Amos Kong <akong@redhat.com>, Dave Gilbert <dgilbert@redhat.com>

On Thu, May 08, 2014 at 12:51:05PM +0000, Zhanghailiang wrote:
> > If you implement this in the net layer then that problem is easy to resolve since
> > we can flush all queues when the guest resumes to get packets flowing again.
> > 
> Do you mean we should also listen for VM runstate changes in net layer, and when detect runstate changes back to running , we flush all queues actively? Am I misunderstanding? 
> Or we can do it *before* qemu (exactly when it check if it can send packets) send packets to guest again, this way will be simple, but it also need know the change of runstate. Any idea? 

When the runstate changes back to running, we definitely need to flush
queues to get packets flowing again.  I think the simplest way of doing
that is in the net layer so individual NICs and netdevs don't have to
duplicate this code.

Stefan