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From: Nicholas Thomas <nick@bytemark.co.uk>
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Date: Thu, 16 May 2013 09:20:55 +0100
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Subject: Re: [Qemu-devel] tap devices not receiving packets from a bridge
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, Peter Lieven <pl@dlhnet.de>, qemu-devel@nongnu.org, netdev@vger.kernel.org

Hi,

On Thu, 2013-05-16 at 09:27 +0300, Michael S. Tsirkin wrote:
> On Thu, May 16, 2013 at 09:24:05AM +0300, Michael S. Tsirkin wrote:
> > Is this with or without vhost-net in host?
> 
> never mind, I see it's without.
> Try to enable vhost-net (you'll have to switch to -netdev syntax
> for that to work) and see if this help.
> If it does it's likely a qemu bug if not probably a guest bug.

Switching to -netdev is non-trivial for me, unfortunately. Anyway, it's
definitely a qemu bug - it happens on kernels 3.2 and 3.9 with 1.4.1,
but doesn't happen with qemu 0.15.0 or 1.5.0rc1.

I'll have a dig through git to see if I can identify the patch that
resolves it. It feels-like qemu sometimes stops reading from the tap
file descriptor between ipxe exiting and the linux kernel bringing up
the network interface, and never recovers from that.

/Nick