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Date: Fri, 10 Jul 2015 00:42:57 +0200
From: Aurelien Jarno <aurelien@aurel32.net>
Message-ID: <20150709224257.GA11298@aurel32.net>
References: <1434113861-26495-1-git-send-email-stefanha@redhat.com>
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Subject: Re: [Qemu-devel] [PULL 05/16] tap: Drop tap_can_send
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To: Fam Zheng <famz@redhat.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>, Christian Borntraeger <borntraeger@de.ibm.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>, Alexander Graf <agraf@suse.de>

On 2015-06-12 13:57, Stefan Hajnoczi wrote:
> From: Fam Zheng <famz@redhat.com>
> 
> This callback is called by main loop before polling s->fd, if it returns
> false, the fd will not be polled in this iteration.
> 
> This is redundant with checks inside read callback. After this patch,
> the data will be sent to peer when it arrives. If the device can't
> receive, it will be queued to incoming_queue, and when the device status
> changes, this queue will be flushed.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> Message-id: 1433400324-7358-7-git-send-email-famz@redhat.com
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  net/tap.c | 13 ++-----------
>  1 file changed, 2 insertions(+), 11 deletions(-)

I just gave a try to QEMU 2.4.0-rc0 with an s390x target, and it seems
this patch breaks virtio-net with a tap device (it works well with the
user mode network stack). The guest correctly sends out packets, but it
seems to not get incoming packets.

This is with TCG, I don't know if KVM is also affected.

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net