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Date: Wed, 22 Sep 2010 12:41:03 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] BUG - qdev - partial loss of network connectivity
References: <20100922171832.GA28721@moo.pl>
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To: Leszek Urbanski <tygrys@moo.pl>
Cc: qemu-devel@nongnu.org

On 09/22/2010 12:18 PM, Leszek Urbanski wrote:
> Hi,
>
> This is a qemu-kvm (i.e. not qemu) bug report. I've been told on IRC (#kvm)
> that this bug report should go to this list anyway.
>
>
> host and guest kernel: 2.6.32.22
> arch: amd64
> qemu-kvm: 0.12.5 and 0.13.0-rc1
>
> How to reproduce: copy a large (few hundred MB) file to an NFS mount
> (guest is the client), using qdev syntax for virtio:
>
> -device virtio-net-pci,netdev=tap1,mac=ab:cd:ef:01:23:45 \
> -netdev type=tap,id=tap1,ifname=tap1
>
> all NFS mounts immediately stall and processes go into D state and are stuck
> on nfs_wait_bit_uninterruptible. There is no further communication between
> the client and the server. It occurs with UDP and TCP mounts.
>
> That same guest, when switched to the old -net/-net syntax:
>
> -net nic,vlan=0,model=virtio,name=eth0,macaddr=ab:cd:ef:01:23:45 \
> -net tap,vlan=0,ifname=tap1
>
> works fine. It also works fine on bare metal.
>
> I can reproduce the problem every time within 10 minutes with qdev.
>    

Is the guest kernel vanilla 2.6.32.22 or is it a distro kernel?  If the 
later, what distro?

The difference in the two invocations is that with the -device syntax, 
you're getting offload features enabled.

Regards,

Anthony Liguori